Split out sized buffer type and added tests. Modified reader to better utilise sized buffer. Debugged and working at least as well as previous.

SizedBuffer/SizedBuffer.h

@@ -0,0 +1,81 @@
+#pragma once
+
+// Guards for C++ usage
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <string.h>
+#include <stdbool.h>
+
+/* A sized buffer abstraction.
+ * 
+ * Functions that return int's will return 0 on success and nonzero otherwise.
+ */
+
+typedef struct sized_buf SizedBuf;
+
+struct sized_buf 
+{
+        char *data;
+        size_t size;
+};
+
+// Returns 0 if the given buffer has at least size bytes available
+inline int sb_check(const SizedBuf sb, const size_t size) 
+{
+        return !(sb.size >= size);
+}
+
+// Moves the buffer size bytes forward, makes no checks
+inline void sb_update(SizedBuf *const sb, const size_t size) 
+{
+        sb->data += size;
+        sb->size -= size;
+}
+
+// Copies size bytes of data from the source to the buffer
+inline int sb_copyin(SizedBuf *const sb, const char *const source, const size_t size) 
+{
+        int ret = sb_check(*sb, size);
+        if (!ret) {
+                memcpy(sb->data, source, size);
+                sb_update(sb, size);
+        }
+        return ret;
+}
+
+// "Recasts" size bytes of memory and returns a pointer to said memory in out
+inline int sb_recast(SizedBuf *const sb, const size_t size, const void **const out) 
+{
+        int ret = sb_check(*sb, size);
+        if (!ret) {
+                *out = sb->data;
+                sb_update(sb, size);
+        }
+        return ret;
+}
+
+// "Recasts" size bytes of memory without actually consuming the buffer
+inline int sb_peek(const SizedBuf sb, const size_t size, const void **const out) 
+{
+        *out = sb.data;
+        return sb_check(sb, size);
+}
+
+// Returns a pointer just after the end of the sized buffer
+inline char *sb_end(const SizedBuf sb) 
+{
+        return sb.data + sb.size;
+}
+
+inline bool sb_empty(const SizedBuf sb) 
+{
+        return sb.size == 0;
+}
+
+// End C++ guard
+#ifdef __cplusplus
+}
+#endif
+