Add 'file_open' for abstracting 'stdin' and 'stdout' checking

Support specifying 'stdin' as "-".

Author: 8dcc

src/file.c

@@ -18,14 +18,37 @@
 
 #include <stdint.h>
 #include <stddef.h>
-#include <stdio.h>
 #include <assert.h>
+#include <stdio.h>
+#include <string.h>
 
 #include "include/file.h"
 #include "include/args.h"
 #include "include/byte_array.h"
 #include "include/util.h"
 
+#define STDIN_FILENAME  "-"
+#define STDOUT_FILENAME "-"
+
+FILE* file_open(const char* path, enum EFileOpenMode mode) {
+    switch (mode) {
+        case FILE_MODE_READ:
+            if (strcmp(path, STDIN_FILENAME) == 0)
+                return stdin;
+            else
+                return fopen(path, "rb");
+
+        case FILE_MODE_WRITE:
+            if (strcmp(path, STDOUT_FILENAME) == 0)
+                return stdout;
+            else
+                return fopen(path, "wb");
+
+        default:
+            DIE("Invalid mode enumerator. Aborting.");
+    }
+}
+
 bool file_read(ByteArray* dst,
                FILE* fp,
                size_t offset_start,

src/include/file.h

@@ -25,6 +25,26 @@
 
 #include "byte_array.h"
 
+/*
+ * Enumeration with the available modes for opening files.
+ */
+enum EFileOpenMode {
+    FILE_MODE_READ,
+    FILE_MODE_WRITE,
+};
+
+/*----------------------------------------------------------------------------*/
+
+/*
+ * Open the file at the specified path with the specified mode. This function
+ * supports special strings for specifying 'stdin' and 'stdout', defined in
+ * 'file.c'.
+ *
+ * The caller is responsible for checking if this function returns NULL in case
+ * of error.
+ */
+FILE* file_open(const char* path, enum EFileOpenMode mode);
+
 /*
  * Read the bytes of a file in a linear way from the starting offset to the end
  * offset. This function returns true on success, or false otherwise.

src/main.c

@@ -34,11 +34,8 @@ int main(int argc, char** argv) {
     args_init(&args);
     args_parse(&args, argc, argv);
 
-    /*
-     * Open the input for reading.
-     * TODO: Support "-" as a filename for standard input.
-     */
-    FILE* input_fp = fopen(args.input_filename, "rb");
+    /* Open the input for reading */
+    FILE* input_fp = file_open(args.input_filename, FILE_MODE_READ);
     if (input_fp == NULL)
         DIE("Can't open file '%s': %s", args.input_filename, strerror(errno));
 
@@ -67,9 +64,7 @@ int main(int argc, char** argv) {
         image_transform_squares(image, args.transform_squares_side);
 
     /* Open the output file for writing */
-    FILE* output_fp = (strcmp(args.output_filename, "-") == 0)
-                        ? stdout
-                        : fopen(args.output_filename, "wb");
+    FILE* output_fp = file_open(args.output_filename, FILE_MODE_WRITE);
     if (output_fp == NULL)
         DIE("Can't open file '%s': %s", args.output_filename, strerror(errno));