X-Git-Url: https://plomlompom.com/repos/?a=blobdiff_plain;f=src%2Freadwrite.c;h=2b6823adfa9bee472eb70ed9474371b607d8b46e;hb=ad3f7d4d420b5447d756be1eaaf78f0abd1a5f65;hp=9f089ea34da821394313b4b81835f5e10ed158c0;hpb=2653efdf1ee13bae3357e0c2964b77588d95b27b;p=plomrogue

diff --git a/src/readwrite.c b/src/readwrite.c
index 9f089ea..2b6823a 100644
--- a/src/readwrite.c
+++ b/src/readwrite.c
@@ -1,37 +1,109 @@
-#include <stdio.h>
-#include <limits.h>
-#include <stdint.h>
-
-static const uint16_t uchar_s = UCHAR_MAX + 1;
-
-extern uint16_t read_uint16_bigendian(FILE * file) {
-// Read uint16 from file in big-endian order.
-  unsigned char a = fgetc(file);
-  unsigned char b = fgetc(file);
-  return (a * uchar_s) + b; }
-
-extern void write_uint16_bigendian(uint16_t x, FILE * file) {
-// Write uint16 to file in beg-endian order.
-  unsigned char a = x / uchar_s;
-  unsigned char b = x % uchar_s;
-  fputc(a, file);
-  fputc(b, file); }
-
-extern uint32_t read_uint32_bigendian(FILE * file) {
-// Read uint32 from file in big-endian order.
-  unsigned char a = fgetc(file);
-  unsigned char b = fgetc(file);
-  unsigned char c = fgetc(file);
-  unsigned char d = fgetc(file);
-  return (a * uchar_s * uchar_s * uchar_s) + (b * uchar_s * uchar_s) + (c * uchar_s) + d; }
-
-extern void write_uint32_bigendian(uint32_t x, FILE * file) {
-// Write uint32 to file in beg-endian order.
-  unsigned char a = x / (uchar_s * uchar_s * uchar_s);
-  unsigned char b = (x - (a * uchar_s * uchar_s * uchar_s)) / (uchar_s * uchar_s);
-  unsigned char c = (x - ((a * uchar_s * uchar_s * uchar_s) + (b * uchar_s * uchar_s))) / uchar_s;
-  unsigned char d = x % uchar_s;
-  fputc(a, file);
-  fputc(b, file);
-  fputc(c, file);
-  fputc(d, file); }
+/* readwrite.c */
+
+#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. */
+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;
+    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)
+{
+    if (0 != size % 8)
+    {
+        return 1;
+    }
+    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, work
+     * on values of fewer bytes corrupts their immediate neighbor bytes. This
+     * necessitates working on newly acquired separate memory areas (* y), only
+     * copying the sufficiently small end result to * x.
+     */
+    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)
+{
+    /* See read_uint8() introductory comment for rationale. */
+    uint32_t y = * x;
+    uint8_t err = read_uintX_bigendian(file, &y, 16);
+    * x = (uint16_t) y;
+    return err;
+}
+
+
+
+extern uint8_t read_uint32_bigendian(FILE * file, uint32_t * x)
+{
+    return read_uintX_bigendian(file, x, 32);
+}
+
+
+
+extern uint8_t write_uint8(uint8_t x, FILE * file)
+{
+    return write_uintX_bigendian(file, x, 8);
+}
+
+
+
+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)
+{
+    return write_uintX_bigendian(file, x, 32);
+}