minor: DIFF determination

use gdiff on SunOS

doc/educational_decoder/Makefile

@@ -7,8 +7,15 @@
 # in the COPYING file in the root directory of this source tree).
 # ################################################################
 
-ZSTD ?= zstd   # requires zstd installation on local system
+ZSTD ?= zstd   # note: requires zstd installation on local system
+
+UNAME?= $(shell uname)
+ifeq ($(UNAME), SunOS)
+DIFF ?= gdiff
+else
 DIFF ?= diff
+endif
+
 HARNESS_FILES=*.c
 
 MULTITHREAD_LDFLAGS = -pthread
@@ -30,7 +37,7 @@ harness: $(HARNESS_FILES)
 
 clean:
 	@$(RM) harness
-	@$(RM) -rf harness.dSYM
+	@$(RM) -rf harness.dSYM  # MacOS specific
 
 test: harness
 	#
@@ -46,7 +53,8 @@ test: harness
 	# note : files are presented multiple for training, to reach minimum threshold
 	@$(ZSTD) --train harness.c zstd_decompress.c zstd_decompress.h README.md \
                   harness.c zstd_decompress.c zstd_decompress.h README.md \
-                  harness.c zstd_decompress.c zstd_decompress.h README.md
+                  harness.c zstd_decompress.c zstd_decompress.h README.md \
+                  -o dictionary
 	@$(ZSTD) -f README.md -D dictionary -o tmp.zst
 	@./harness tmp.zst tmp dictionary
 	@$(DIFF) -s tmp README.md

doc/educational_decoder/harness.c

@@ -25,15 +25,16 @@ u8 *input;
 u8 *output;
 u8 *dict;
 
-size_t read_file(const char *path, u8 **ptr) {
+static size_t read_file(const char *path, u8 **ptr)
-    FILE *f = fopen(path, "rb");
+{
+    FILE* const f = fopen(path, "rb");
     if (!f) {
         fprintf(stderr, "failed to open file %s \n", path);
         exit(1);
     }
 
     fseek(f, 0L, SEEK_END);
-    size_t size = (size_t)ftell(f);
+    size_t const size = (size_t)ftell(f);
     rewind(f);
 
     *ptr = malloc(size);
@@ -44,7 +45,7 @@ size_t read_file(const char *path, u8 **ptr) {
 
     size_t pos = 0;
     while (!feof(f)) {
-        size_t read = fread(&(*ptr)[pos], 1, size, f);
+        size_t const read = fread(*ptr + pos, 1, size, f);
         if (ferror(f)) {
             fprintf(stderr, "error while reading file %s \n", path);
             exit(1);
@@ -57,17 +58,17 @@ size_t read_file(const char *path, u8 **ptr) {
     return pos;
 }
 
-void write_file(const char *path, const u8 *ptr, size_t size) {
+static void write_file(const char *path, const u8 *ptr, size_t size)
-    FILE *f = fopen(path, "wb");
+{
+    FILE* const f = fopen(path, "wb");
 
     size_t written = 0;
     while (written < size) {
-        written += fwrite(&ptr[written], 1, size, f);
+        written += fwrite(ptr+written, 1, size, f);
         if (ferror(f)) {
             fprintf(stderr, "error while writing file %s\n", path);
             exit(1);
-        }
+    }   }
-    }
 
     fclose(f);
 }
@@ -80,7 +81,7 @@ int main(int argc, char **argv) {
         return 1;
     }
 
-    size_t input_size = read_file(argv[1], &input);
+    size_t const input_size = read_file(argv[1], &input);
     size_t dict_size = 0;
     if (argc >= 4) {
         dict_size = read_file(argv[3], &dict);
@@ -92,8 +93,8 @@ int main(int argc, char **argv) {
         fprintf(stderr, "WARNING: Compressed data does not contain "
                         "decompressed size, going to assume the compression "
                         "ratio is at most %d (decompressed size of at most "
-                        "%zu)\n",
+                        "%u) \n",
-                MAX_COMPRESSION_RATIO, decompressed_size);
+                MAX_COMPRESSION_RATIO, (unsigned)decompressed_size);
     }
     if (decompressed_size > MAX_OUTPUT_SIZE) {
         fprintf(stderr,
@@ -122,4 +123,5 @@ int main(int argc, char **argv) {
     free(output);
     free(dict);
     input = output = dict = NULL;
+    return 0;
 }