X-Git-Url: https://plomlompom.com/repos/?a=blobdiff_plain;f=src%2Freadwrite.c;h=5b318524619d53180055f8aafbc489f9292827e5;hb=c8ff28bbc9394d2788bc9d106f1375c6c7836f34;hp=449e96b4c3d5d5051e08d9d45a13864870ca9513;hpb=27cee0624f3dc430199c99f000179a3385e4d7c5;p=plomrogue

diff --git a/src/readwrite.c b/src/readwrite.c
index 449e96b..5b31852 100644
--- a/src/readwrite.c
+++ b/src/readwrite.c
@@ -1,37 +1,110 @@
-/*  readwrite.c */
+/* readwrite.c */
 
 #include "readwrite.h"
-#include <stdio.h>
-#include <stdint.h>
+#include <stdio.h> /* for FILE typedef*/
+#include <stdint.h> /* for uint8_t, uint16_t, uint32_t */
 
-extern uint16_t read_uint16_bigendian( FILE * file )
+
+
+/* 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)
+{
+    * x = 0;
+    int16_t bitshift = size - 8;
+    int test;
+    for (; bitshift >= 0; bitshift = bitshift - 8)
+    {
+        test = fgetc(file);
+        if (EOF == test)
+        {
+            return 1;
+        }
+        * x = * x + ((uint32_t) test << bitshift);
+    }
+    return 0;
+}
+
+
+
+static uint8_t write_uintX_bigendian(FILE * file, uint32_t x, uint8_t size)
+{
+    int16_t bitshift = size - 8;
+    for (; bitshift >= 0; bitshift = bitshift - 8)
+    {
+        if (EOF == fputc((x >> bitshift) & 0xFF, file))
+        {
+            return 1;
+        }
+    }
+    return 0;
+}
+
+
+
+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 err = read_uintX_bigendian(file, &y, 8);
+    * x = (uint8_t) y;
+    return err;
+}
+
+
+
+extern uint8_t read_uint16_bigendian(FILE * file, uint16_t * x)
 {
-    uint16_t x;
-    x =     (uint16_t) fgetc(file) << 8;
-    x = x + (uint16_t) fgetc(file);
-    return x;
+    /* See read_uint8() introductory code comment for rationale. */
+    uint32_t y = * x;
+    uint8_t err = read_uintX_bigendian(file, &y, 16);
+    * x = (uint16_t) y;
+    return err;
 }
 
-extern uint32_t read_uint32_bigendian( FILE * file )
+
+
+extern uint8_t read_uint32_bigendian(FILE * file, uint32_t * x)
 {
-    uint32_t x;
-    x =       (uint32_t) fgetc(file) << 24;
-    x = x + ( (uint32_t) fgetc(file) << 16 );
-    x = x + ( (uint32_t) fgetc(file) <<  8 );
-    x = x +   (uint32_t) fgetc(file);
-    return x;
+    return read_uintX_bigendian(file, x, 32);
 }
 
-extern void write_uint16_bigendian( uint16_t x, FILE * file )
+
+
+extern uint8_t write_uint8(uint8_t x, FILE * file)
 {
-    fputc( x >> 8,   file );
-    fputc( x & 0xFF, file );
+    return write_uintX_bigendian(file, x, 8);
 }
 
-extern void write_uint32_bigendian( uint32_t x, FILE * file )
+
+
+extern uint8_t write_uint16_bigendian(uint16_t x, FILE * file)
+{
+    return write_uintX_bigendian(file, x, 16);
+}
+
+
+
+extern uint8_t write_uint32_bigendian(uint32_t x, FILE * file)
 {
-    fputc(   x >> 24,          file);
-    fputc( ( x >> 16 ) & 0xFF, file);
-    fputc( ( x >>  8 ) & 0xFF, file);
-    fputc(   x         & 0xFF, file);
+    return write_uintX_bigendian(file, x, 32);
 }