1 files changed, 1377 insertions, 0 deletions

diff --git a/utils/rbutilqt/mspack/chmd.c b/utils/rbutilqt/mspack/chmd.c
new file mode 100644
index 0000000000..6c8481db14
--- /dev/null
+++ b/utils/rbutilqt/mspack/chmd.c
@@ -0,0 +1,1377 @@
+/* This file is part of libmspack.
+ * (C) 2003-2018 Stuart Caie.
+ *
+ * libmspack is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License (LGPL) version 2.1
+ *
+ * For further details, see the file COPYING.LIB distributed with libmspack
+ */
+
+/* CHM decompression implementation */
+
+#include "system-mspack.h"
+#include "chm.h"
+
+/* prototypes */
+static struct mschmd_header * chmd_open(
+  struct mschm_decompressor *base, const char *filename);
+static struct mschmd_header * chmd_fast_open(
+  struct mschm_decompressor *base, const char *filename);
+static struct mschmd_header *chmd_real_open(
+  struct mschm_decompressor *base, const char *filename, int entire);
+static void chmd_close(
+  struct mschm_decompressor *base, struct mschmd_header *chm);
+static int chmd_read_headers(
+  struct mspack_system *sys, struct mspack_file *fh,
+  struct mschmd_header *chm, int entire);
+static int chmd_fast_find(
+  struct mschm_decompressor *base, struct mschmd_header *chm,
+  const char *filename, struct mschmd_file *f_ptr, int f_size);
+static unsigned char *read_chunk(
+  struct mschm_decompressor_p *self, struct mschmd_header *chm,
+  struct mspack_file *fh, unsigned int chunk);
+static int search_chunk(
+  struct mschmd_header *chm, const unsigned char *chunk, const char *filename,
+  const unsigned char **result, const unsigned char **result_end);
+static inline int compare(
+  const char *s1, const char *s2, int l1, int l2);
+static int chmd_extract(
+  struct mschm_decompressor *base, struct mschmd_file *file,
+  const char *filename);
+static int chmd_sys_write(
+  struct mspack_file *file, void *buffer, int bytes);
+static int chmd_init_decomp(
+  struct mschm_decompressor_p *self, struct mschmd_file *file);
+static int read_reset_table(
+  struct mschm_decompressor_p *self, struct mschmd_sec_mscompressed *sec,
+  unsigned int entry, off_t *length_ptr, off_t *offset_ptr);
+static int read_spaninfo(
+  struct mschm_decompressor_p *self, struct mschmd_sec_mscompressed *sec,
+  off_t *length_ptr);
+static int find_sys_file(
+  struct mschm_decompressor_p *self, struct mschmd_sec_mscompressed *sec,
+  struct mschmd_file **f_ptr, const char *name);
+static unsigned char *read_sys_file(
+  struct mschm_decompressor_p *self, struct mschmd_file *file);
+static int chmd_error(
+  struct mschm_decompressor *base);
+static int read_off64(
+  off_t *var, unsigned char *mem, struct mspack_system *sys,
+  struct mspack_file *fh);
+
+/* filenames of the system files used for decompression.
+ * Content and ControlData are essential.
+ * ResetTable is preferred, but SpanInfo can be used if not available
+ */
+static const char *content_name  = "::DataSpace/Storage/MSCompressed/Content";
+static const char *control_name  = "::DataSpace/Storage/MSCompressed/ControlData";
+static const char *spaninfo_name = "::DataSpace/Storage/MSCompressed/SpanInfo";
+static const char *rtable_name   = "::DataSpace/Storage/MSCompressed/Transform/"
+  "{7FC28940-9D31-11D0-9B27-00A0C91E9C7C}/InstanceData/ResetTable";
+
+/***************************************
+ * MSPACK_CREATE_CHM_DECOMPRESSOR
+ ***************************************
+ * constructor
+ */
+struct mschm_decompressor *
+  mspack_create_chm_decompressor(struct mspack_system *sys)
+{
+  struct mschm_decompressor_p *self = NULL;
+
+  if (!sys) sys = mspack_default_system;
+  if (!mspack_valid_system(sys)) return NULL;
+
+  if ((self = (struct mschm_decompressor_p *) sys->alloc(sys, sizeof(struct mschm_decompressor_p)))) {
+    self->base.open       = &chmd_open;
+    self->base.close      = &chmd_close;
+    self->base.extract    = &chmd_extract;
+    self->base.last_error = &chmd_error;
+    self->base.fast_open  = &chmd_fast_open;
+    self->base.fast_find  = &chmd_fast_find;
+    self->system          = sys;
+    self->error           = MSPACK_ERR_OK;
+    self->d               = NULL;
+  }
+  return (struct mschm_decompressor *) self;
+}
+
+/***************************************
+ * MSPACK_DESTROY_CAB_DECOMPRESSOR
+ ***************************************
+ * destructor
+ */
+void mspack_destroy_chm_decompressor(struct mschm_decompressor *base) {
+  struct mschm_decompressor_p *self = (struct mschm_decompressor_p *) base;
+  if (self) {
+    struct mspack_system *sys = self->system;
+    if (self->d) {
+      if (self->d->infh)  sys->close(self->d->infh);
+      if (self->d->state) lzxd_free(self->d->state);
+      sys->free(self->d);
+    }
+    sys->free(self);
+  }
+}
+
+/***************************************
+ * CHMD_OPEN
+ ***************************************
+ * opens a file and tries to read it as a CHM file.
+ * Calls chmd_real_open() with entire=1.
+ */
+static struct mschmd_header *chmd_open(struct mschm_decompressor *base,
+                                       const char *filename)
+{
+  return chmd_real_open(base, filename, 1);
+}
+
+/***************************************
+ * CHMD_FAST_OPEN
+ ***************************************
+ * opens a file and tries to read it as a CHM file, but does not read
+ * the file headers. Calls chmd_real_open() with entire=0
+ */
+static struct mschmd_header *chmd_fast_open(struct mschm_decompressor *base,
+                                            const char *filename)
+{
+  return chmd_real_open(base, filename, 0);
+}
+
+/***************************************
+ * CHMD_REAL_OPEN
+ ***************************************
+ * the real implementation of chmd_open() and chmd_fast_open(). It simply
+ * passes the "entire" parameter to chmd_read_headers(), which will then
+ * either read all headers, or a bare mininum.
+ */
+static struct mschmd_header *chmd_real_open(struct mschm_decompressor *base,
+                                            const char *filename, int entire)
+{
+  struct mschm_decompressor_p *self = (struct mschm_decompressor_p *) base;
+  struct mschmd_header *chm = NULL;
+  struct mspack_system *sys;
+  struct mspack_file *fh;
+  int error;
+
+  if (!base) return NULL;
+  sys = self->system;
+
+  if ((fh = sys->open(sys, filename, MSPACK_SYS_OPEN_READ))) {
+    if ((chm = (struct mschmd_header *) sys->alloc(sys, sizeof(struct mschmd_header)))) {
+      chm->filename = filename;
+      error = chmd_read_headers(sys, fh, chm, entire);
+      if (error) {
+        /* if the error is DATAFORMAT, and there are some results, return
+         * partial results with a warning, rather than nothing */
+        if (error == MSPACK_ERR_DATAFORMAT && (chm->files || chm->sysfiles)) {
+          sys->message(fh, "WARNING; contents are corrupt");
+          error = MSPACK_ERR_OK;
+        }
+        else {
+          chmd_close(base, chm);
+          chm = NULL;
+        }
+      }
+      self->error = error;
+    }
+    else {
+      self->error = MSPACK_ERR_NOMEMORY;
+    }
+    sys->close(fh);
+  }
+  else {
+    self->error = MSPACK_ERR_OPEN;
+  }
+  return chm;
+}
+
+/***************************************
+ * CHMD_CLOSE
+ ***************************************
+ * frees all memory associated with a given mschmd_header
+ */
+static void chmd_close(struct mschm_decompressor *base,
+                       struct mschmd_header *chm)
+{
+  struct mschm_decompressor_p *self = (struct mschm_decompressor_p *) base;
+  struct mschmd_file *fi, *nfi;
+  struct mspack_system *sys;
+  unsigned int i;
+
+  if (!base) return;
+  sys = self->system;
+
+  self->error = MSPACK_ERR_OK;
+
+  /* free files */
+  for (fi = chm->files; fi; fi = nfi) {
+    nfi = fi->next;
+    sys->free(fi);
+  }
+  for (fi = chm->sysfiles; fi; fi = nfi) {
+    nfi = fi->next;
+    sys->free(fi);
+  }
+
+  /* if this CHM was being decompressed, free decompression state */
+  if (self->d && (self->d->chm == chm)) {
+    if (self->d->infh) sys->close(self->d->infh);
+    if (self->d->state) lzxd_free(self->d->state);
+    sys->free(self->d);
+    self->d = NULL;
+  }
+
+  /* if this CHM had a chunk cache, free it and contents */
+  if (chm->chunk_cache) {
+      for (i = 0; i < chm->num_chunks; i++) sys->free(chm->chunk_cache[i]);
+      sys->free(chm->chunk_cache);
+  }
+
+  sys->free(chm);
+}
+
+/***************************************
+ * CHMD_READ_HEADERS
+ ***************************************
+ * reads the basic CHM file headers. If the "entire" parameter is
+ * non-zero, all file entries will also be read. fills out a pre-existing
+ * mschmd_header structure, allocates memory for files as necessary
+ */
+
+/* The GUIDs found in CHM headers */
+static const unsigned char guids[32] = {
+  /* {7C01FD10-7BAA-11D0-9E0C-00A0-C922-E6EC} */
+  0x10, 0xFD, 0x01, 0x7C, 0xAA, 0x7B, 0xD0, 0x11,
+  0x9E, 0x0C, 0x00, 0xA0, 0xC9, 0x22, 0xE6, 0xEC,
+  /* {7C01FD11-7BAA-11D0-9E0C-00A0-C922-E6EC} */
+  0x11, 0xFD, 0x01, 0x7C, 0xAA, 0x7B, 0xD0, 0x11,
+  0x9E, 0x0C, 0x00, 0xA0, 0xC9, 0x22, 0xE6, 0xEC
+};
+
+/* reads an encoded integer into a variable; 7 bits of data per byte,
+ * the high bit is used to indicate that there is another byte */
+#define READ_ENCINT(var) do {                   \
+    (var) = 0;                                  \
+    do {                                        \
+        if (p >= end) goto chunk_end;           \
+        (var) = ((var) << 7) | (*p & 0x7F);     \
+    } while (*p++ & 0x80);                      \
+} while (0)
+
+static int chmd_read_headers(struct mspack_system *sys, struct mspack_file *fh,
+                             struct mschmd_header *chm, int entire)
+{
+  unsigned int section, name_len, x, errors, num_chunks;
+  unsigned char buf[0x54], *chunk = NULL, *name, *p, *end;
+  struct mschmd_file *fi, *link = NULL;
+  off_t offset, length;
+  int num_entries;
+
+  /* initialise pointers */
+  chm->files         = NULL;
+  chm->sysfiles      = NULL;
+  chm->chunk_cache   = NULL;
+  chm->sec0.base.chm = chm;
+  chm->sec0.base.id  = 0;
+  chm->sec1.base.chm = chm;
+  chm->sec1.base.id  = 1;
+  chm->sec1.content  = NULL;
+  chm->sec1.control  = NULL;
+  chm->sec1.spaninfo = NULL;
+  chm->sec1.rtable   = NULL;
+
+  /* read the first header */
+  if (sys->read(fh, &buf[0], chmhead_SIZEOF) != chmhead_SIZEOF) {
+    return MSPACK_ERR_READ;
+  }
+
+  /* check ITSF signature */
+  if (EndGetI32(&buf[chmhead_Signature]) != 0x46535449) {
+    return MSPACK_ERR_SIGNATURE;
+  }
+
+  /* check both header GUIDs */
+  if (memcmp(&buf[chmhead_GUID1], &guids[0], 32L) != 0) {
+    D(("incorrect GUIDs"))
+    return MSPACK_ERR_SIGNATURE;
+  }
+
+  chm->version   = EndGetI32(&buf[chmhead_Version]);
+  chm->timestamp = EndGetM32(&buf[chmhead_Timestamp]);
+  chm->language  = EndGetI32(&buf[chmhead_LanguageID]);
+  if (chm->version > 3) {
+    sys->message(fh, "WARNING; CHM version > 3");
+  }
+
+  /* read the header section table */
+  if (sys->read(fh, &buf[0], chmhst3_SIZEOF) != chmhst3_SIZEOF) {
+    return MSPACK_ERR_READ;
+  }
+
+  /* chmhst3_OffsetCS0 does not exist in version 1 or 2 CHM files.
+   * The offset will be corrected later, once HS1 is read.
+   */
+  if (read_off64(&offset,           &buf[chmhst_OffsetHS0],  sys, fh) ||
+      read_off64(&chm->dir_offset,  &buf[chmhst_OffsetHS1],  sys, fh) ||
+      read_off64(&chm->sec0.offset, &buf[chmhst3_OffsetCS0], sys, fh))
+  {
+    return MSPACK_ERR_DATAFORMAT;
+  }
+
+  /* seek to header section 0 */
+  if (sys->seek(fh, offset, MSPACK_SYS_SEEK_START)) {
+    return MSPACK_ERR_SEEK;
+  }
+
+  /* read header section 0 */
+  if (sys->read(fh, &buf[0], chmhs0_SIZEOF) != chmhs0_SIZEOF) {
+    return MSPACK_ERR_READ;
+  }
+  if (read_off64(&chm->length, &buf[chmhs0_FileLen], sys, fh)) {
+    return MSPACK_ERR_DATAFORMAT;
+  }
+
+  /* seek to header section 1 */
+  if (sys->seek(fh, chm->dir_offset, MSPACK_SYS_SEEK_START)) {
+    return MSPACK_ERR_SEEK;
+  }
+
+  /* read header section 1 */
+  if (sys->read(fh, &buf[0], chmhs1_SIZEOF) != chmhs1_SIZEOF) {
+    return MSPACK_ERR_READ;
+  }
+
+  chm->dir_offset = sys->tell(fh);
+  chm->chunk_size = EndGetI32(&buf[chmhs1_ChunkSize]);
+  chm->density    = EndGetI32(&buf[chmhs1_Density]);
+  chm->depth      = EndGetI32(&buf[chmhs1_Depth]);
+  chm->index_root = EndGetI32(&buf[chmhs1_IndexRoot]);
+  chm->num_chunks = EndGetI32(&buf[chmhs1_NumChunks]);
+  chm->first_pmgl = EndGetI32(&buf[chmhs1_FirstPMGL]);
+  chm->last_pmgl  = EndGetI32(&buf[chmhs1_LastPMGL]);
+
+  if (chm->version < 3) {
+    /* versions before 3 don't have chmhst3_OffsetCS0 */
+    chm->sec0.offset = chm->dir_offset + (chm->chunk_size * chm->num_chunks);
+  }
+
+  /* check if content offset or file size is wrong */
+  if (chm->sec0.offset > chm->length) {
+    D(("content section begins after file has ended"))
+    return MSPACK_ERR_DATAFORMAT;
+  }
+  
+  /* ensure there are chunks and that chunk size is
+   * large enough for signature and num_entries */
+  if (chm->chunk_size < (pmgl_Entries + 2)) {
+    D(("chunk size not large enough"))
+    return MSPACK_ERR_DATAFORMAT;
+  }
+  if (chm->num_chunks == 0) {
+    D(("no chunks"))
+    return MSPACK_ERR_DATAFORMAT;
+  }
+
+  /* The chunk_cache data structure is not great; large values for num_chunks
+   * or num_chunks*chunk_size can exhaust all memory. Until a better chunk
+   * cache is implemented, put arbitrary limits on num_chunks and chunk size.
+   */
+  if (chm->num_chunks > 100000) {
+    D(("more than 100,000 chunks"))
+    return MSPACK_ERR_DATAFORMAT;
+  }
+  if (chm->chunk_size > 8192) {
+    D(("chunk size over 8192 (get in touch if this is valid)"))
+    return MSPACK_ERR_DATAFORMAT;
+  }
+  if ((off_t)chm->chunk_size * (off_t)chm->num_chunks > chm->length) {
+    D(("chunks larger than entire file"))
+    return MSPACK_ERR_DATAFORMAT;
+  }
+
+  /* common sense checks on header section 1 fields */
+  if (chm->chunk_size != 4096) {
+    sys->message(fh, "WARNING; chunk size is not 4096");
+  }
+  if (chm->first_pmgl != 0) {
+    sys->message(fh, "WARNING; first PMGL chunk is not zero");
+  }
+  if (chm->first_pmgl > chm->last_pmgl) {
+    D(("first pmgl chunk is after last pmgl chunk"))
+    return MSPACK_ERR_DATAFORMAT;
+  }
+  if (chm->index_root != 0xFFFFFFFF && chm->index_root >= chm->num_chunks) {
+    D(("index_root outside valid range"))
+    return MSPACK_ERR_DATAFORMAT;
+  }
+
+  /* if we are doing a quick read, stop here! */
+  if (!entire) {
+    return MSPACK_ERR_OK;
+  }
+
+  /* seek to the first PMGL chunk, and reduce the number of chunks to read */
+  if ((x = chm->first_pmgl) != 0) {
+    if (sys->seek(fh,(off_t) (x * chm->chunk_size), MSPACK_SYS_SEEK_CUR)) {
+      return MSPACK_ERR_SEEK;
+    }
+  }
+  num_chunks = chm->last_pmgl - x + 1;
+
+  if (!(chunk = (unsigned char *) sys->alloc(sys, (size_t)chm->chunk_size))) {
+    return MSPACK_ERR_NOMEMORY;
+  }
+
+  /* read and process all chunks from FirstPMGL to LastPMGL */
+  errors = 0;
+  while (num_chunks--) {
+    /* read next chunk */
+    if (sys->read(fh, chunk, (int)chm->chunk_size) != (int)chm->chunk_size) {
+      sys->free(chunk);
+      return MSPACK_ERR_READ;
+    }
+
+    /* process only directory (PMGL) chunks */
+    if (EndGetI32(&chunk[pmgl_Signature]) != 0x4C474D50) continue;
+
+    if (EndGetI32(&chunk[pmgl_QuickRefSize]) < 2) {
+      sys->message(fh, "WARNING; PMGL quickref area is too small");
+    }
+    if (EndGetI32(&chunk[pmgl_QuickRefSize]) > 
+        (chm->chunk_size - pmgl_Entries))
+    {
+      sys->message(fh, "WARNING; PMGL quickref area is too large");
+    }
+
+    p = &chunk[pmgl_Entries];
+    end = &chunk[chm->chunk_size - 2];
+    num_entries = EndGetI16(end);
+
+    while (num_entries--) {
+      READ_ENCINT(name_len);
+      if (name_len > (unsigned int) (end - p)) goto chunk_end;
+      name = p; p += name_len;
+      READ_ENCINT(section);
+      READ_ENCINT(offset);
+      READ_ENCINT(length);
+
+      /* ignore blank or one-char (e.g. "/") filenames we'd return as blank */
+      if (name_len < 2 || !name[0] || !name[1]) continue;
+
+      /* empty files and directory names are stored as a file entry at
+       * offset 0 with length 0. We want to keep empty files, but not
+       * directory names, which end with a "/" */
+      if ((offset == 0) && (length == 0)) {
+        if ((name_len > 0) && (name[name_len-1] == '/')) continue;
+      }
+
+      if (section > 1) {
+        sys->message(fh, "invalid section number '%u'.", section);
+        continue;
+      }
+
+      if (!(fi = (struct mschmd_file *) sys->alloc(sys, sizeof(struct mschmd_file) + name_len + 1))) {
+        sys->free(chunk);
+        return MSPACK_ERR_NOMEMORY;
+      }
+
+      fi->next     = NULL;
+      fi->filename = (char *) &fi[1];
+      fi->section  = ((section == 0) ? (struct mschmd_section *) (&chm->sec0)
+                                     : (struct mschmd_section *) (&chm->sec1));
+      fi->offset   = offset;
+      fi->length   = length;
+      sys->copy(name, fi->filename, (size_t) name_len);
+      fi->filename[name_len] = '\0';
+
+      if (name[0] == ':' && name[1] == ':') {
+        /* system file */
+        if (name_len == 40 && memcmp(name, content_name, 40) == 0) {
+          chm->sec1.content = fi;
+        }
+        else if (name_len == 44 && memcmp(name, control_name, 44) == 0) {
+          chm->sec1.control = fi;
+        }
+        else if (name_len == 41 && memcmp(name, spaninfo_name, 41) == 0) {
+          chm->sec1.spaninfo = fi;
+        }
+        else if (name_len == 105 && memcmp(name, rtable_name, 105) == 0) {
+          chm->sec1.rtable = fi;
+        }
+        fi->next = chm->sysfiles;
+        chm->sysfiles = fi;
+      }
+      else {
+        /* normal file */
+        if (link) link->next = fi; else chm->files = fi;
+        link = fi;
+      }
+    }
+
+    /* this is reached either when num_entries runs out, or if
+     * reading data from the chunk reached a premature end of chunk */
+  chunk_end:
+    if (num_entries >= 0) {
+      D(("chunk ended before all entries could be read"))
+      errors++;
+    }
+
+  }
+  sys->free(chunk);
+  return (errors > 0) ? MSPACK_ERR_DATAFORMAT : MSPACK_ERR_OK;
+}
+
+/***************************************
+ * CHMD_FAST_FIND
+ ***************************************
+ * uses PMGI index chunks and quickref data to quickly locate a file
+ * directly from the on-disk index.
+ *
+ * TODO: protect against infinite loops in chunks (where pgml_NextChunk
+ * or a PMGI index entry point to an already visited chunk)
+ */
+static int chmd_fast_find(struct mschm_decompressor *base,
+                          struct mschmd_header *chm, const char *filename,
+                          struct mschmd_file *f_ptr, int f_size)
+{
+    struct mschm_decompressor_p *self = (struct mschm_decompressor_p *) base;
+    struct mspack_system *sys;
+    struct mspack_file *fh;
+    /* p and end are initialised to prevent MSVC warning about "potentially"
+     * uninitialised usage. This is provably untrue, but MS won't fix:
+     * https://developercommunity.visualstudio.com/content/problem/363489/c4701-false-positive-warning.html */
+    const unsigned char *chunk, *p = NULL, *end = NULL;
+    int err = MSPACK_ERR_OK, result = -1;
+    unsigned int n, sec;
+
+    if (!self || !chm || !f_ptr || (f_size != sizeof(struct mschmd_file))) {
+        return MSPACK_ERR_ARGS;
+    }
+    sys = self->system;
+
+    /* clear the results structure */
+    memset(f_ptr, 0, f_size);
+
+    if (!(fh = sys->open(sys, chm->filename, MSPACK_SYS_OPEN_READ))) {
+        return MSPACK_ERR_OPEN;
+    }
+
+    /* go through PMGI chunk hierarchy to reach PMGL chunk */
+    if (chm->index_root < chm->num_chunks) {
+        n = chm->index_root;
+        for (;;) {
+            if (!(chunk = read_chunk(self, chm, fh, n))) {
+                sys->close(fh);
+                return self->error;
+            }
+
+            /* search PMGI/PMGL chunk. exit early if no entry found */
+            if ((result = search_chunk(chm, chunk, filename, &p, &end)) <= 0) {
+                break;
+            }
+
+            /* found result. loop around for next chunk if this is PMGI */
+            if (chunk[3] == 0x4C) break; else READ_ENCINT(n);
+        }
+    }
+    else {
+        /* PMGL chunks only, search from first_pmgl to last_pmgl */
+        for (n = chm->first_pmgl; n <= chm->last_pmgl;
+             n = EndGetI32(&chunk[pmgl_NextChunk]))
+        {
+            if (!(chunk = read_chunk(self, chm, fh, n))) {
+                err = self->error;
+                break;
+            }
+
+            /* search PMGL chunk. exit if file found */
+            if ((result = search_chunk(chm, chunk, filename, &p, &end)) > 0) {
+                break;
+            }
+
+            /* stop simple infinite loops: can't visit the same chunk twice */
+            if (n == EndGetI32(&chunk[pmgl_NextChunk])) {
+                break;
+            }
+        }
+    }
+
+    /* if we found a file, read it */
+    if (result > 0) {
+        READ_ENCINT(sec);
+        f_ptr->section  = (sec == 0) ? (struct mschmd_section *) &chm->sec0
+                                     : (struct mschmd_section *) &chm->sec1;
+        READ_ENCINT(f_ptr->offset);
+        READ_ENCINT(f_ptr->length);
+    }
+    else if (result < 0) {
+        err = MSPACK_ERR_DATAFORMAT;
+    }
+
+    sys->close(fh);
+    return self->error = err;
+
+ chunk_end:
+    D(("read beyond end of chunk entries"))
+    sys->close(fh);
+    return self->error = MSPACK_ERR_DATAFORMAT;
+}
+
+/* reads the given chunk into memory, storing it in a chunk cache
+ * so it doesn't need to be read from disk more than once
+ */
+static unsigned char *read_chunk(struct mschm_decompressor_p *self,
+                                 struct mschmd_header *chm,
+                                 struct mspack_file *fh,
+                                 unsigned int chunk_num)
+{
+    struct mspack_system *sys = self->system;
+    unsigned char *buf;
+
+    /* check arguments - most are already checked by chmd_fast_find */
+    if (chunk_num >= chm->num_chunks) return NULL;
+    
+    /* ensure chunk cache is available */
+    if (!chm->chunk_cache) {
+        size_t size = sizeof(unsigned char *) * chm->num_chunks;
+        if (!(chm->chunk_cache = (unsigned char **) sys->alloc(sys, size))) {
+            self->error = MSPACK_ERR_NOMEMORY;
+            return NULL;
+        }
+        memset(chm->chunk_cache, 0, size);
+    }
+
+    /* try to answer out of chunk cache */
+    if (chm->chunk_cache[chunk_num]) return chm->chunk_cache[chunk_num];
+
+    /* need to read chunk - allocate memory for it */
+    if (!(buf = (unsigned char *) sys->alloc(sys, chm->chunk_size))) {
+        self->error = MSPACK_ERR_NOMEMORY;
+        return NULL;
+    }
+
+    /* seek to block and read it */
+    if (sys->seek(fh, (off_t) (chm->dir_offset + (chunk_num * chm->chunk_size)),
+                      MSPACK_SYS_SEEK_START))
+    {
+        self->error = MSPACK_ERR_SEEK;
+        sys->free(buf);
+        return NULL;
+    }
+    if (sys->read(fh, buf, (int)chm->chunk_size) != (int)chm->chunk_size) {
+        self->error = MSPACK_ERR_READ;
+        sys->free(buf);
+        return NULL;
+    }
+
+    /* check the signature. Is is PMGL or PMGI? */
+    if (!((buf[0] == 0x50) && (buf[1] == 0x4D) && (buf[2] == 0x47) &&
+          ((buf[3] == 0x4C) || (buf[3] == 0x49))))
+    {
+        self->error = MSPACK_ERR_SEEK;
+        sys->free(buf);
+        return NULL;
+    }
+
+    /* all OK. Store chunk in cache and return it */
+    return chm->chunk_cache[chunk_num] = buf;
+}
+
+/* searches a PMGI/PMGL chunk for a given filename entry. Returns -1 on
+ * data format error, 0 if entry definitely not found, 1 if entry
+ * found. In the latter case, *result and *result_end are set pointing
+ * to that entry's data (either the "next chunk" ENCINT for a PMGI or
+ * the section, offset and length ENCINTs for a PMGL).
+ *
+ * In the case of PMGL chunks, the entry has definitely been
+ * found. In the case of PMGI chunks, the entry which points to the
+ * chunk that may eventually contain that entry has been found.
+ */
+static int search_chunk(struct mschmd_header *chm,
+                        const unsigned char *chunk,
+                        const char *filename,
+                        const unsigned char **result,
+                        const unsigned char **result_end)
+{
+    const unsigned char *start, *end, *p;
+    unsigned int qr_size, num_entries, qr_entries, qr_density, name_len;
+    unsigned int L, R, M, fname_len, entries_off, is_pmgl;
+    int cmp;
+
+    fname_len = strlen(filename);
+
+    /* PMGL chunk or PMGI chunk? (note: read_chunk() has already
+     * checked the rest of the characters in the chunk signature) */
+    if (chunk[3] == 0x4C) {
+        is_pmgl = 1;
+        entries_off = pmgl_Entries;
+    }
+    else {
+        is_pmgl = 0;
+        entries_off = pmgi_Entries;
+    }
+
+    /*  Step 1: binary search first filename of each QR entry
+     *  - target filename == entry
+     *    found file
+     *  - target filename < all entries
+     *    file not found
+     *  - target filename > all entries
+     *    proceed to step 2 using final entry
+     *  - target filename between two searched entries
+     *    proceed to step 2
+     */
+    qr_size     = EndGetI32(&chunk[pmgl_QuickRefSize]);
+    start       = &chunk[chm->chunk_size - 2];
+    end         = &chunk[chm->chunk_size - qr_size];
+    num_entries = EndGetI16(start);
+    qr_density  = 1 + (1 << chm->density);
+    qr_entries  = (num_entries + qr_density-1) / qr_density;
+
+    if (num_entries == 0) {
+        D(("chunk has no entries"))
+        return -1;
+    }
+
+    if (qr_size > chm->chunk_size) {
+        D(("quickref size > chunk size"))
+        return -1;
+    }
+
+    *result_end = end;
+
+    if (((int)qr_entries * 2) > (start - end)) {
+        D(("WARNING; more quickrefs than quickref space"))
+        qr_entries = 0; /* but we can live with it */
+    }
+
+    if (qr_entries > 0) {
+        L = 0;
+        R = qr_entries - 1;
+        do {
+            /* pick new midpoint */
+            M = (L + R) >> 1;
+
+            /* compare filename with entry QR points to */
+            p = &chunk[entries_off + (M ? EndGetI16(start - (M << 1)) : 0)];
+            READ_ENCINT(name_len);
+            if (name_len > (unsigned int) (end - p)) goto chunk_end;
+            cmp = compare(filename, (char *)p, fname_len, name_len);
+
+            if (cmp == 0) break;
+            else if (cmp < 0) { if (M) R = M - 1; else return 0; }
+            else if (cmp > 0) L = M + 1;
+        } while (L <= R);
+        M = (L + R) >> 1;
+
+        if (cmp == 0) {
+            /* exact match! */
+            p += name_len;
+            *result = p;
+            return 1;
+        }
+
+        /* otherwise, read the group of entries for QR entry M */
+        p = &chunk[entries_off + (M ? EndGetI16(start - (M << 1)) : 0)];
+        num_entries -= (M * qr_density);
+        if (num_entries > qr_density) num_entries = qr_density;
+    }
+    else {
+        p = &chunk[entries_off];
+    }
+
+    /* Step 2: linear search through the set of entries reached in step 1.
+     * - filename == any entry
+     *   found entry
+     * - filename < all entries (PMGI) or any entry (PMGL)
+     *   entry not found, stop now
+     * - filename > all entries
+     *   entry not found (PMGL) / maybe found (PMGI)
+     * - 
+     */
+    *result = NULL;
+    while (num_entries-- > 0) {
+        READ_ENCINT(name_len);
+        if (name_len > (unsigned int) (end - p)) goto chunk_end;
+        cmp = compare(filename, (char *)p, fname_len, name_len);
+        p += name_len;
+
+        if (cmp == 0) {
+            /* entry found */
+            *result = p;
+            return 1;
+        }
+
+        if (cmp < 0) {
+            /* entry not found (PMGL) / maybe found (PMGI) */
+            break;
+        }
+
+        /* read and ignore the rest of this entry */
+        if (is_pmgl) {
+            READ_ENCINT(R); /* skip section */
+            READ_ENCINT(R); /* skip offset */
+            READ_ENCINT(R); /* skip length */
+        }
+        else {
+            *result = p; /* store potential final result */
+            READ_ENCINT(R); /* skip chunk number */
+        }
+    }
+
+     /* PMGL? not found. PMGI? maybe found */
+     return (is_pmgl) ? 0 : (*result ? 1 : 0);
+
+ chunk_end:
+    D(("reached end of chunk data while searching"))
+    return -1;
+}
+
+#if HAVE_TOWLOWER
+# include <wctype.h>
+# define TOLOWER(x) towlower(x)
+#else
+# include <ctype.h>
+# define TOLOWER(x) tolower(x)
+#endif
+
+/* decodes a UTF-8 character from s[] into c. Will not read past e. 
+ * doesn't test that extension bytes are %10xxxxxx.
+ * allows some overlong encodings.
+ */
+#define GET_UTF8_CHAR(s, e, c) do {                                     \
+    unsigned char x = *s++;                                             \
+    if (x < 0x80) c = x;                                                \
+    else if (x >= 0xC2 && x < 0xE0 && s < e) {                          \
+        c = (x & 0x1F) << 6 | (*s++ & 0x3F);                            \
+    }                                                                   \
+    else if (x >= 0xE0 && x < 0xF0 && s+1 < e) {                        \
+        c = (x & 0x0F) << 12 | (s[0] & 0x3F) << 6 | (s[1] & 0x3F);      \
+        s += 2;                                                         \
+    }                                                                   \
+    else if (x >= 0xF0 && x <= 0xF5 && s+2 < e) {                       \
+        c = (x & 0x07) << 18 | (s[0] & 0x3F) << 12 |                    \
+            (s[1] & 0x3F) << 6 | (s[2] & 0x3F);                         \
+        if (c > 0x10FFFF) c = 0xFFFD;                                   \
+        s += 3;                                                         \
+    }                                                                   \
+    else c = 0xFFFD;                                                    \
+} while (0)
+
+/* case-insensitively compares two UTF8 encoded strings. String length for
+ * both strings must be provided, null bytes are not terminators */
+static inline int compare(const char *s1, const char *s2, int l1, int l2) {
+    register const unsigned char *p1 = (const unsigned char *) s1;
+    register const unsigned char *p2 = (const unsigned char *) s2;
+    register const unsigned char *e1 = p1 + l1, *e2 = p2 + l2;
+    int c1, c2;
+
+    while (p1 < e1 && p2 < e2) {
+        GET_UTF8_CHAR(p1, e1, c1);
+        GET_UTF8_CHAR(p2, e2, c2);
+        if (c1 == c2) continue;
+        c1 = TOLOWER(c1);
+        c2 = TOLOWER(c2);
+        if (c1 != c2) return c1 - c2;
+    }
+    return l1 - l2;
+}
+
+
+/***************************************
+ * CHMD_EXTRACT
+ ***************************************
+ * extracts a file from a CHM helpfile
+ */
+static int chmd_extract(struct mschm_decompressor *base,
+                        struct mschmd_file *file, const char *filename)
+{
+  struct mschm_decompressor_p *self = (struct mschm_decompressor_p *) base;
+  struct mspack_system *sys;
+  struct mschmd_header *chm;
+  struct mspack_file *fh;
+  off_t bytes;
+
+  if (!self) return MSPACK_ERR_ARGS;
+  if (!file || !file->section) return self->error = MSPACK_ERR_ARGS;
+  sys = self->system;
+  chm = file->section->chm;
+
+  /* create decompression state if it doesn't exist */
+  if (!self->d) {
+    self->d = (struct mschmd_decompress_state *) sys->alloc(sys, sizeof(struct mschmd_decompress_state));
+    if (!self->d) return self->error = MSPACK_ERR_NOMEMORY;
+    self->d->chm       = chm;
+    self->d->offset    = 0;
+    self->d->state     = NULL;
+    self->d->sys       = *sys;
+    self->d->sys.write = &chmd_sys_write;
+    self->d->infh      = NULL;
+    self->d->outfh     = NULL;
+  }
+
+  /* open input chm file if not open, or the open one is a different chm */
+  if (!self->d->infh || (self->d->chm != chm)) {
+    if (self->d->infh)  sys->close(self->d->infh);
+    if (self->d->state) lzxd_free(self->d->state);
+    self->d->chm    = chm;
+    self->d->offset = 0;
+    self->d->state  = NULL;
+    self->d->infh   = sys->open(sys, chm->filename, MSPACK_SYS_OPEN_READ);
+    if (!self->d->infh) return self->error = MSPACK_ERR_OPEN;
+  }
+
+  /* open file for output */
+  if (!(fh = sys->open(sys, filename, MSPACK_SYS_OPEN_WRITE))) {
+    return self->error = MSPACK_ERR_OPEN;
+  }
+
+  /* if file is empty, simply creating it is enough */
+  if (!file->length) {
+    sys->close(fh);
+    return self->error = MSPACK_ERR_OK;
+  }
+
+  self->error = MSPACK_ERR_OK;
+
+  switch (file->section->id) {
+  case 0: /* Uncompressed section file */
+    /* simple seek + copy */
+    if (sys->seek(self->d->infh, file->section->chm->sec0.offset
+                  + file->offset, MSPACK_SYS_SEEK_START))
+    {
+      self->error = MSPACK_ERR_SEEK;
+    }
+    else {
+      unsigned char buf[512];
+      off_t length = file->length;
+      while (length > 0) {
+        int run = sizeof(buf);
+        if ((off_t)run > length) run = (int)length;
+        if (sys->read(self->d->infh, &buf[0], run) != run) {
+          self->error = MSPACK_ERR_READ;
+          break;
+        }
+        if (sys->write(fh, &buf[0], run) != run) {
+          self->error = MSPACK_ERR_WRITE;
+          break;
+        }
+        length -= run;
+      }
+    }
+    break;
+
+  case 1: /* MSCompressed section file */
+    /* (re)initialise compression state if we it is not yet initialised,
+     * or we have advanced too far and have to backtrack
+     */
+    if (!self->d->state || (file->offset < self->d->offset)) {
+      if (self->d->state) {
+        lzxd_free(self->d->state);
+        self->d->state = NULL;
+      }
+      if (chmd_init_decomp(self, file)) break;
+    }
+
+    /* seek to input data */
+    if (sys->seek(self->d->infh, self->d->inoffset, MSPACK_SYS_SEEK_START)) {
+      self->error = MSPACK_ERR_SEEK;
+      break;
+    }
+
+    /* get to correct offset. */
+    self->d->outfh = NULL;
+    if ((bytes = file->offset - self->d->offset)) {
+      self->error = lzxd_decompress(self->d->state, bytes);
+    }
+
+    /* if getting to the correct offset was error free, unpack file */
+    if (!self->error) {
+      self->d->outfh = fh;
+      self->error = lzxd_decompress(self->d->state, file->length);
+    }
+
+    /* save offset in input source stream, in case there is a section 0
+     * file between now and the next section 1 file extracted */
+    self->d->inoffset = sys->tell(self->d->infh);
+
+    /* if an LZX error occured, the LZX decompressor is now useless */
+    if (self->error) {
+      if (self->d->state) lzxd_free(self->d->state);
+      self->d->state = NULL;
+    }
+    break;
+  }
+
+  sys->close(fh);
+  return self->error;
+}
+
+/***************************************
+ * CHMD_SYS_WRITE
+ ***************************************
+ * chmd_sys_write is the internal writer function which the decompressor
+ * uses. If either writes data to disk (self->d->outfh) with the real
+ * sys->write() function, or does nothing with the data when
+ * self->d->outfh == NULL. advances self->d->offset.
+ */
+static int chmd_sys_write(struct mspack_file *file, void *buffer, int bytes) {
+  struct mschm_decompressor_p *self = (struct mschm_decompressor_p *) file;
+  self->d->offset += bytes;
+  if (self->d->outfh) {
+    return self->system->write(self->d->outfh, buffer, bytes);
+  }
+  return bytes;
+}
+
+/***************************************
+ * CHMD_INIT_DECOMP
+ ***************************************
+ * Initialises the LZX decompressor to decompress the compressed stream,
+ * from the nearest reset offset and length that is needed for the given
+ * file.
+ */
+static int chmd_init_decomp(struct mschm_decompressor_p *self,
+                            struct mschmd_file *file)
+{
+  int window_size, window_bits, reset_interval, entry, err;
+  struct mspack_system *sys = self->system;
+  struct mschmd_sec_mscompressed *sec;
+  unsigned char *data;
+  off_t length, offset;
+
+  sec = (struct mschmd_sec_mscompressed *) file->section;
+
+  /* ensure we have a mscompressed content section */
+  err = find_sys_file(self, sec, &sec->content, content_name);
+  if (err) return self->error = err;
+
+  /* ensure we have a ControlData file */
+  err = find_sys_file(self, sec, &sec->control, control_name);
+  if (err) return self->error = err;
+
+  /* read ControlData */
+  if (sec->control->length < lzxcd_SIZEOF) {
+    D(("ControlData file is too short"))
+    return self->error = MSPACK_ERR_DATAFORMAT;
+  }
+  if (!(data = read_sys_file(self, sec->control))) {
+    D(("can't read mscompressed control data file"))
+    return self->error;
+  }
+
+  /* check LZXC signature */
+  if (EndGetI32(&data[lzxcd_Signature]) != 0x43585A4C) {
+    sys->free(data);
+    return self->error = MSPACK_ERR_SIGNATURE;
+  }
+
+  /* read reset_interval and window_size and validate version number */
+  switch (EndGetI32(&data[lzxcd_Version])) {
+  case 1:
+    reset_interval = EndGetI32(&data[lzxcd_ResetInterval]);
+    window_size    = EndGetI32(&data[lzxcd_WindowSize]);
+    break;
+  case 2:
+    reset_interval = EndGetI32(&data[lzxcd_ResetInterval]) * LZX_FRAME_SIZE;
+    window_size    = EndGetI32(&data[lzxcd_WindowSize])    * LZX_FRAME_SIZE;
+    break;
+  default:
+    D(("bad controldata version"))
+    sys->free(data);
+    return self->error = MSPACK_ERR_DATAFORMAT;
+  }
+
+  /* free ControlData */
+  sys->free(data);
+
+  /* find window_bits from window_size */
+  switch (window_size) {
+  case 0x008000: window_bits = 15; break;
+  case 0x010000: window_bits = 16; break;
+  case 0x020000: window_bits = 17; break;
+  case 0x040000: window_bits = 18; break;
+  case 0x080000: window_bits = 19; break;
+  case 0x100000: window_bits = 20; break;
+  case 0x200000: window_bits = 21; break;
+  default:
+    D(("bad controldata window size"))
+    return self->error = MSPACK_ERR_DATAFORMAT;
+  }
+
+  /* validate reset_interval */
+  if (reset_interval == 0 || reset_interval % LZX_FRAME_SIZE) {
+    D(("bad controldata reset interval"))
+    return self->error = MSPACK_ERR_DATAFORMAT;
+  }
+
+  /* which reset table entry would we like? */
+  entry = file->offset / reset_interval;
+  /* convert from reset interval multiple (usually 64k) to 32k frames */
+  entry *= reset_interval / LZX_FRAME_SIZE;
+
+  /* read the reset table entry */
+  if (read_reset_table(self, sec, entry, &length, &offset)) {
+    /* the uncompressed length given in the reset table is dishonest.
+     * the uncompressed data is always padded out from the given
+     * uncompressed length up to the next reset interval */
+    length += reset_interval - 1;
+    length &= -reset_interval;
+  }
+  else {
+    /* if we can't read the reset table entry, just start from
+     * the beginning. Use spaninfo to get the uncompressed length */
+    entry = 0;
+    offset = 0;
+    err = read_spaninfo(self, sec, &length);
+  }
+  if (err) return self->error = err;
+
+  /* get offset of compressed data stream:
+   * = offset of uncompressed section from start of file
+   * + offset of compressed stream from start of uncompressed section
+   * + offset of chosen reset interval from start of compressed stream */
+  self->d->inoffset = file->section->chm->sec0.offset + sec->content->offset + offset;
+
+  /* set start offset and overall remaining stream length */
+  self->d->offset = entry * LZX_FRAME_SIZE;
+  length -= self->d->offset;
+
+  /* initialise LZX stream */
+  self->d->state = lzxd_init(&self->d->sys, self->d->infh,
+                             (struct mspack_file *) self, window_bits,
+                             reset_interval / LZX_FRAME_SIZE,
+                             4096, length, 0);
+  if (!self->d->state) self->error = MSPACK_ERR_NOMEMORY;
+  return self->error;
+}
+
+/***************************************
+ * READ_RESET_TABLE
+ ***************************************
+ * Reads one entry out of the reset table. Also reads the uncompressed
+ * data length. Writes these to offset_ptr and length_ptr respectively.
+ * Returns non-zero for success, zero for failure.
+ */
+static int read_reset_table(struct mschm_decompressor_p *self,
+                            struct mschmd_sec_mscompressed *sec,
+                            unsigned int entry,
+                            off_t *length_ptr, off_t *offset_ptr)
+{
+    struct mspack_system *sys = self->system;
+    unsigned char *data;
+    unsigned int pos, entrysize;
+
+    /* do we have a ResetTable file? */
+    int err = find_sys_file(self, sec, &sec->rtable, rtable_name);
+    if (err) return 0;
+
+    /* read ResetTable file */
+    if (sec->rtable->length < lzxrt_headerSIZEOF) {
+        D(("ResetTable file is too short"))
+        return 0;
+    }
+    if (!(data = read_sys_file(self, sec->rtable))) {
+        D(("can't read reset table"))
+        return 0;
+    }
+
+    /* check sanity of reset table */
+    if (EndGetI32(&data[lzxrt_FrameLen]) != LZX_FRAME_SIZE) {
+        D(("bad reset table frame length"))
+        sys->free(data);
+        return 0;
+    }
+
+    /* get the uncompressed length of the LZX stream */
+    if (read_off64(length_ptr, &data[lzxrt_UncompLen], sys, self->d->infh)) {
+        sys->free(data);
+        return 0;
+    }
+
+    entrysize = EndGetI32(&data[lzxrt_EntrySize]);
+    pos = EndGetI32(&data[lzxrt_TableOffset]) + (entry * entrysize);
+
+    /* ensure reset table entry for this offset exists */
+    if (entry < EndGetI32(&data[lzxrt_NumEntries]) &&
+        pos <= (sec->rtable->length - entrysize))
+    {
+        switch (entrysize) {
+        case 4:
+            *offset_ptr = EndGetI32(&data[pos]);
+            err = 0;
+            break;
+        case 8:
+            err = read_off64(offset_ptr, &data[pos], sys, self->d->infh);
+            break;
+        default:
+            D(("reset table entry size neither 4 nor 8"))
+            err = 1;
+            break;
+        }
+    }
+    else {
+        D(("bad reset interval"))
+        err = 1;
+    }
+
+    /* free the reset table */
+    sys->free(data);
+
+    /* return success */
+    return (err == 0);
+}
+
+/***************************************
+ * READ_SPANINFO
+ ***************************************
+ * Reads the uncompressed data length from the spaninfo file.
+ * Returns zero for success or a non-zero error code for failure.
+ */
+static int read_spaninfo(struct mschm_decompressor_p *self,
+                         struct mschmd_sec_mscompressed *sec,
+                         off_t *length_ptr)
+{
+    struct mspack_system *sys = self->system;
+    unsigned char *data;
+    
+    /* find SpanInfo file */
+    int err = find_sys_file(self, sec, &sec->spaninfo, spaninfo_name);
+    if (err) return MSPACK_ERR_DATAFORMAT;
+
+    /* check it's large enough */
+    if (sec->spaninfo->length != 8) {
+        D(("SpanInfo file is wrong size"))
+        return MSPACK_ERR_DATAFORMAT;
+    }
+
+    /* read the SpanInfo file */
+    if (!(data = read_sys_file(self, sec->spaninfo))) {
+        D(("can't read SpanInfo file"))
+        return self->error;
+    }
+
+    /* get the uncompressed length of the LZX stream */
+    err = read_off64(length_ptr, data, sys, self->d->infh);
+    sys->free(data);
+    if (err) return MSPACK_ERR_DATAFORMAT;
+
+    if (*length_ptr <= 0) {
+        D(("output length is invalid"))
+        return MSPACK_ERR_DATAFORMAT;
+    }
+
+    return MSPACK_ERR_OK;
+}
+
+/***************************************
+ * FIND_SYS_FILE
+ ***************************************
+ * Uses chmd_fast_find to locate a system file, and fills out that system
+ * file's entry and links it into the list of system files. Returns zero
+ * for success, non-zero for both failure and the file not existing.
+ */
+static int find_sys_file(struct mschm_decompressor_p *self,
+                         struct mschmd_sec_mscompressed *sec,
+                         struct mschmd_file **f_ptr, const char *name)
+{
+    struct mspack_system *sys = self->system;
+    struct mschmd_file result;
+
+    /* already loaded */
+    if (*f_ptr) return MSPACK_ERR_OK;
+
+    /* try using fast_find to find the file - return DATAFORMAT error if
+     * it fails, or successfully doesn't find the file */
+    if (chmd_fast_find((struct mschm_decompressor *) self, sec->base.chm,
+                       name, &result, (int)sizeof(result)) || !result.section)
+    {
+        return MSPACK_ERR_DATAFORMAT;
+    }
+
+    if (!(*f_ptr = (struct mschmd_file *) sys->alloc(sys, sizeof(result)))) {
+        return MSPACK_ERR_NOMEMORY;
+    }
+
+    /* copy result */
+    *(*f_ptr) = result;
+    (*f_ptr)->filename = (char *) name;
+
+    /* link file into sysfiles list */
+    (*f_ptr)->next = sec->base.chm->sysfiles;
+    sec->base.chm->sysfiles = *f_ptr;
+    return MSPACK_ERR_OK;
+}
+
+/***************************************
+ * READ_SYS_FILE
+ ***************************************
+ * Allocates memory for a section 0 (uncompressed) file and reads it into
+ * memory.
+ */
+static unsigned char *read_sys_file(struct mschm_decompressor_p *self,
+                                    struct mschmd_file *file)
+{
+  struct mspack_system *sys = self->system;
+  unsigned char *data = NULL;
+  int len;
+
+  if (!file || !file->section || (file->section->id != 0)) {
+    self->error = MSPACK_ERR_DATAFORMAT;
+    return NULL;
+  }
+
+  len = (int) file->length;
+
+  if (!(data = (unsigned char *) sys->alloc(sys, (size_t) len))) {
+    self->error = MSPACK_ERR_NOMEMORY;
+    return NULL;
+  }
+  if (sys->seek(self->d->infh, file->section->chm->sec0.offset
+                + file->offset, MSPACK_SYS_SEEK_START))
+  {
+    self->error = MSPACK_ERR_SEEK;
+    sys->free(data);
+    return NULL;
+  }
+  if (sys->read(self->d->infh, data, len) != len) {
+    self->error = MSPACK_ERR_READ;
+    sys->free(data);
+    return NULL;
+  }
+  return data;
+}
+
+/***************************************
+ * CHMD_ERROR
+ ***************************************
+ * returns the last error that occurred
+ */
+static int chmd_error(struct mschm_decompressor *base) {
+  struct mschm_decompressor_p *self = (struct mschm_decompressor_p *) base;
+  return (self) ? self->error : MSPACK_ERR_ARGS;
+}
+
+/***************************************
+ * READ_OFF64
+ ***************************************
+ * Reads a 64-bit signed integer from memory in Intel byte order.
+ * If running on a system with a 64-bit off_t, this is simply done.
+ * If running on a system with a 32-bit off_t, offsets up to 0x7FFFFFFF
+ * are accepted, offsets beyond that cause an error message.
+ */
+static int read_off64(off_t *var, unsigned char *mem,
+                      struct mspack_system *sys, struct mspack_file *fh)
+{
+#if LARGEFILE_SUPPORT
+    *var = EndGetI64(mem);
+#else
+    *var = EndGetI32(mem);
+    if ((*var & 0x80000000) || EndGetI32(mem+4)) {
+        sys->message(fh, (char *)largefile_msg);
+        return 1;
+    }
+#endif
+    return 0;
+}