refactor of harness, for clarity (#1974)

following #1953 (false positive, due to heuristic confusion)

doc/educational_decoder/harness.c

@@ -21,108 +21,93 @@ typedef unsigned char u8;
 // Protect against allocating too much memory for output
 #define MAX_OUTPUT_SIZE ((size_t)1024 * 1024 * 1024)
 
-static size_t read_file(const char *path, u8 **ptr)
+// Error message then exit
+#define ERR_OUT(...) { fprintf(stderr, __VA_ARGS__); exit(1); }
+
+
+typedef struct {
+    u8* address;
+    size_t size;
+} buffer_s;
+
+static void freeBuffer(buffer_s b) { free(b.address); }
+
+static buffer_s read_file(const char *path)
 {
     FILE* const f = fopen(path, "rb");
-    if (!f) {
-        fprintf(stderr, "failed to open file %s \n", path);
-        exit(1);
-    }
+    if (!f) ERR_OUT("failed to open file %s \n", path);
 
     fseek(f, 0L, SEEK_END);
     size_t const size = (size_t)ftell(f);
     rewind(f);
 
-    *ptr = malloc(size);
-    if (!ptr) {
-        fprintf(stderr, "failed to allocate memory to hold %s \n", path);
-        exit(1);
-    }
+    void* const ptr = malloc(size);
+    if (!ptr) ERR_OUT("failed to allocate memory to hold %s \n", path);
 
-    size_t const read = fread(*ptr, 1, size, f);
-    if (read != size) {  /* must read everything in one pass */
-        fprintf(stderr, "error while reading file %s \n", path);
-        exit(1);
-    }
+    size_t const read = fread(ptr, 1, size, f);
+    if (read != size) ERR_OUT("error while reading file %s \n", path);
 
     fclose(f);
-
-    return read;
+    buffer_s const b = { ptr, size };
+    return b;
 }
 
-static 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* const f = fopen(path, "wb");
-    if (!f) {
-        fprintf(stderr, "failed to open file %s \n", path);
-        exit(1);
-    }
+    if (!f) ERR_OUT("failed to open file %s \n", path);
 
     size_t written = 0;
     while (written < size) {
         written += fwrite(ptr+written, 1, size, f);
-        if (ferror(f)) {
-            fprintf(stderr, "error while writing file %s\n", path);
-            exit(1);
-    }   }
+        if (ferror(f)) ERR_OUT("error while writing file %s\n", path);
+    }
 
     fclose(f);
 }
 
 int main(int argc, char **argv)
 {
-    if (argc < 3) {
-        fprintf(stderr, "usage: %s <file.zst> <out_path> [dictionary] \n",
-                argv[0]);
+    if (argc < 3)
+        ERR_OUT("usage: %s <file.zst> <out_path> [dictionary] \n", argv[0]);
 
-        return 1;
-    }
+    buffer_s const input = read_file(argv[1]);
 
-    u8* input;
-    size_t const input_size = read_file(argv[1], &input);
-
-    u8* dict = NULL;
-    size_t dict_size = 0;
+    buffer_s dict = { NULL, 0 };
     if (argc >= 4) {
-        dict_size = read_file(argv[3], &dict);
+        dict = read_file(argv[3]);
     }
 
-    size_t out_capacity = ZSTD_get_decompressed_size(input, input_size);
+    size_t out_capacity = ZSTD_get_decompressed_size(input.address, input.size);
     if (out_capacity == (size_t)-1) {
-        out_capacity = MAX_COMPRESSION_RATIO * input_size;
+        out_capacity = MAX_COMPRESSION_RATIO * input.size;
         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 "
                         "%u) \n",
                 MAX_COMPRESSION_RATIO, (unsigned)out_capacity);
     }
-    if (out_capacity > MAX_OUTPUT_SIZE) {
-        fprintf(stderr,
-                "Required output size too large for this implementation \n");
-        return 1;
-    }
+    if (out_capacity > MAX_OUTPUT_SIZE)
+        ERR_OUT("Required output size too large for this implementation \n");
 
     u8* const output = malloc(out_capacity);
-    if (!output) {
-        fprintf(stderr, "failed to allocate memory \n");
-        return 1;
-    }
+    if (!output) ERR_OUT("failed to allocate memory \n");
 
     dictionary_t* const parsed_dict = create_dictionary();
-    if (dict) {
-        parse_dictionary(parsed_dict, dict, dict_size);
+    if (dict.size) {
+        parse_dictionary(parsed_dict, dict.address, dict.size);
     }
     size_t const decompressed_size =
         ZSTD_decompress_with_dict(output, out_capacity,
-                                  input, input_size,
+                                  input.address, input.size,
                                   parsed_dict);
 
     free_dictionary(parsed_dict);
 
     write_file(argv[2], output, decompressed_size);
 
-    free(input);
+    freeBuffer(input);
+    freeBuffer(dict);
     free(output);
-    free(dict);
     return 0;
 }