Re-add the check for small buffers and a new test (see Blosc/python-blosc2#46)

Author: FrancescAlted

blosc/blosc2.c

@@ -2220,6 +2220,10 @@ static int write_compression_header(blosc2_context* context, bool extended_heade
     /* Compression level 0 means buffer to be memcpy'ed */
     context->header_flags |= (uint8_t)BLOSC_MEMCPYED;
   }
+  if (context->sourcesize < BLOSC_MIN_BUFFERSIZE) {
+    /* Buffer is too small.  Try memcpy'ing. */
+    context->header_flags |= (uint8_t)BLOSC_MEMCPYED;
+  }
 
   bool memcpyed = context->header_flags & (uint8_t)BLOSC_MEMCPYED;
   if (extended_header) {

include/blosc2.h

@@ -173,8 +173,8 @@ enum {
   //!< Maximum typesize before considering source buffer as a stream of bytes.
   //!< Cannot be larger than 255.
 #endif // BLOSC_H
-  BLOSC_MIN_BUFFERSIZE = 128,
-  //!< Minimum buffer size to be compressed. Cannot be smaller than 66.
+  BLOSC_MIN_BUFFERSIZE = 32,
+  //!< Minimum buffer size to be compressed.
 };
 
 

tests/test_compressor.c

@@ -237,6 +237,40 @@ static char *test_small_blocksize(void) {
 }
 
 
+/* Check small buffer */
+static char *test_small_buffer(void) {
+  blosc2_cparams cparams = BLOSC2_CPARAMS_DEFAULTS;
+  cparams.typesize = 1;
+  blosc2_context *cctx = blosc2_create_cctx(cparams);
+  blosc2_dparams dparams = BLOSC2_DPARAMS_DEFAULTS;
+  blosc2_context *dctx = blosc2_create_dctx(dparams);
+  size = 2;
+  uint8_t *src2 = calloc(size, 1);
+  for (int i = 0; i < size; i++) {
+    src2[i] = (uint8_t)i;
+  }
+
+  /* Using contexts */
+  cbytes = blosc2_compress_ctx(cctx, src2, size, dest, size + BLOSC2_MAX_OVERHEAD);
+  nbytes = blosc2_decompress_ctx(dctx, dest, size + BLOSC2_MAX_OVERHEAD, src, size);
+  mu_assert("ERROR: nbytes is not correct", nbytes == size);
+
+  /* Not using contexts */
+  cbytes = blosc2_compress(9, 1, cparams.typesize, src2, size, dest, size + BLOSC2_MAX_OVERHEAD);
+  nbytes = blosc2_decompress(dest, size + BLOSC2_MAX_OVERHEAD, src, size);
+  mu_assert("ERROR: nbytes is not correct", nbytes == size);
+
+  /* Using Blosc1 interface */
+  cbytes = blosc1_compress(9, 1, cparams.typesize, size, src2, dest, size + BLOSC2_MAX_OVERHEAD);
+  nbytes = blosc1_decompress(dest, src, size);
+  mu_assert("ERROR: nbytes is not correct", nbytes == size);
+
+  free(src2);
+  blosc2_free_ctx(cctx);
+  blosc2_free_ctx(dctx);
+  return 0;
+}
+
 
 static char *all_tests(void) {
   mu_run_test(test_compressor);
@@ -248,6 +282,7 @@ static char *all_tests(void) {
   mu_run_test(test_delta);
   mu_run_test(test_typesize);
   mu_run_test(test_small_blocksize);
+  mu_run_test(test_small_buffer);
 
   return 0;
 }