2 files changed, 17 insertions, 4 deletions

diff --git a/firmware/buflib.c b/firmware/buflib.c
index 1aa7404ece..4233bf9a61 100644
--- a/firmware/buflib.c
+++ b/firmware/buflib.c
@@ -724,7 +724,18 @@ buflib_alloc_maximum(struct buflib_context* ctx, const char* name, size_t *size,
     /* limit name to 16 since that's what buflib_available() accounts for it */
     char buf[16];
 
-    *size = buflib_available(ctx);
+    /* ignore ctx->compact because it's true if all movable blocks are contiguous
+     * even if the buffer has holes due to unmovable allocations */
+    unsigned hints;
+    size_t bufsize = ctx->handle_table - ctx->buf_start;
+    bufsize = MIN(BUFLIB_SHRINK_SIZE_MASK, bufsize*sizeof(union buflib_data)); /* make it bytes */
+    /* try as hard as possible to free up space. allocations are
+     * welcome to give up some or all of their memory */
+    hints = BUFLIB_SHRINK_POS_BACK | BUFLIB_SHRINK_POS_FRONT | bufsize;
+    /* compact until no space can be gained anymore */
+    while (buflib_compact_and_shrink(ctx, hints));
+
+    *size = buflib_allocatable(ctx);
     if (*size <= 0) /* OOM */
         return -1;
 
diff --git a/firmware/include/buflib.h b/firmware/include/buflib.h
index 7183951c6c..aa6c232f72 100644
--- a/firmware/include/buflib.h
+++ b/firmware/include/buflib.h
@@ -111,10 +111,10 @@ struct buflib_callbacks {
     void (*sync_callback)(int handle, bool sync_on);
 };
 
-#define BUFLIB_SHRINK_POS_MASK ((1<<0|1<<1)<<30)
 #define BUFLIB_SHRINK_SIZE_MASK (~BUFLIB_SHRINK_POS_MASK)
 #define BUFLIB_SHRINK_POS_FRONT (1u<<31)
 #define BUFLIB_SHRINK_POS_BACK  (1u<<30)
+#define BUFLIB_SHRINK_POS_MASK  (BUFLIB_SHRINK_POS_FRONT|BUFLIB_SHRINK_POS_BACK)
 
 /**
  * Possible return values for the callbacks, some of them can cause
@@ -193,8 +193,10 @@ int buflib_alloc_ex(struct buflib_context *ctx, size_t size, const char *name,
  * will allow buflib to permit allocations by shrinking the buffer returned by
  * this function.
  *
- * Note that this currently gives whatever buflib_available() returns. However,
- * do not depend on this behavior, it may change.
+ * Note that this might return many more bytes than buflib_available() or
+ * buflib_allocatable() return, because it agressively compacts the pool
+ * and even shrinks other allocations. However, do not depend on this behavior,
+ * it may change.
  *
  * name: A string identifier giving this allocation a name
  * size: The actual size will be returned into size