Minor comment clarification.

[plomrogue] / src / readwrite.c

diff --git a/src/readwrite.c b/src/readwrite.c
index 6d24992520b6687a99e91007231d1ec10c455651..5b318524619d53180055f8aafbc489f9292827e5 100644 (file)
--- a/src/readwrite.c
+++ b/src/readwrite.c
@@ -2,25 +2,33 @@
 
 #include "readwrite.h"
 #include <stdio.h> /* for FILE typedef*/
-#include <stdint.h> /* for uint16_t, uint32_t */
-
-
-
-/* Read/write "x" from/to "file" as bigendian representation of "size" bits. */
+#include <stdint.h> /* for uint8_t, uint16_t, uint32_t */
+
+
+
+/* Read/write "x" from/to "file" as bigendian representation of "size" bits. On
+ * failure, return 1, else 0. (As of of now, all extern read/write functions
+ * build on top of these.)
+ *
+ * Only use multiples of 8 greater or equal 32 for "size", so that storage
+ * inside uint32_t is possible. Originally a bit number check prefaced the code
+ * of both functions. It was removed as redundant due to all possible "size"
+ * values being hardcoded into the library (i.e. in all extern functions calling
+ * / wrapping around either function). If this ever changes, (re-)insert:
+ *
+ *    if (0 == size || size > 32 || 0 != size % 8)
+ *    {
+ *        return 1;
+ *    }
+ */
 static uint8_t read_uintX_bigendian(FILE * file, uint32_t * x, uint8_t size);
 static uint8_t write_uintX_bigendian(FILE * file, uint32_t x, uint8_t size);
 
 
-
 static uint8_t read_uintX_bigendian(FILE * file, uint32_t * x, uint8_t size)
 {
-    if (0 != size % 8)
-    {
-        return 1;
-    }
-    int16_t bitshift = size - 8;
-
     * x = 0;
+    int16_t bitshift = size - 8;
     int test;
     for (; bitshift >= 0; bitshift = bitshift - 8)
     {
@@ -38,12 +46,7 @@ static uint8_t read_uintX_bigendian(FILE * file, uint32_t * x, uint8_t size)
 
 static uint8_t write_uintX_bigendian(FILE * file, uint32_t x, uint8_t size)
 {
-    if (0 != size % 8)
-    {
-        return 1;
-    }
     int16_t bitshift = size - 8;
-
     for (; bitshift >= 0; bitshift = bitshift - 8)
     {
         if (EOF == fputc((x >> bitshift) & 0xFF, file))
@@ -58,20 +61,24 @@ static uint8_t write_uintX_bigendian(FILE * file, uint32_t x, uint8_t size)
 
 extern uint8_t read_uint8(FILE * file, uint8_t * x)
 {
+    /* Since read_uintX_bigendian() works on -- and zeroes -- four bytes, direct
+     * work on values of fewer bytes would corrupt immediate neighbor values.
+     */
     uint32_t y = * x;
-    uint8_t fail = read_uintX_bigendian(file, &y, 8);
+    uint8_t err = read_uintX_bigendian(file, &y, 8);
     * x = (uint8_t) y;
-    return fail;
+    return err;
 }
 
 
 
 extern uint8_t read_uint16_bigendian(FILE * file, uint16_t * x)
 {
+    /* See read_uint8() introductory code comment for rationale. */
     uint32_t y = * x;
-    uint8_t fail = read_uintX_bigendian(file, &y, 16);
+    uint8_t err = read_uintX_bigendian(file, &y, 16);
     * x = (uint16_t) y;
-    return fail;
+    return err;
 }