dstring: Split out the dynamic string logic.

1 files changed, 99 insertions, 0 deletions

diff --git a/dstring.c b/dstring.c
new file mode 100644
index 0000000..9c65757
--- /dev/null
+++ b/dstring.c
@@ -0,0 +1,99 @@
+/*********************************************************************
+ * bfs                                                               *
+ * Copyright (C) 2016 Tavian Barnes <tavianator@tavianator.com>      *
+ *                                                                   *
+ * This program is free software. It comes without any warranty, to  *
+ * the extent permitted by applicable law. You can redistribute it   *
+ * and/or modify it under the terms of the Do What The Fuck You Want *
+ * To Public License, Version 2, as published by Sam Hocevar. See    *
+ * the COPYING file or http://www.wtfpl.net/ for more details.       *
+ *********************************************************************/
+
+#include "dstring.h"
+#include <stdlib.h>
+#include <string.h>
+
+/**
+ * The memory representation of a dynamic string.  Users get a pointer to data.
+ */
+struct dstring {
+	size_t capacity;
+	size_t length;
+	char data[];
+};
+
+static struct dstring *dstrheader(const char *dstr) {
+	return (struct dstring *)(dstr - offsetof(struct dstring, data));
+}
+
+static size_t dstrsize(size_t capacity) {
+	return sizeof(struct dstring) + capacity + 1;
+}
+
+char *dstralloc(size_t capacity) {
+	struct dstring *header = malloc(dstrsize(capacity));
+	if (!header) {
+		return NULL;
+	}
+
+	header->capacity = capacity;
+	header->length = 0;
+	return header->data;
+}
+
+size_t dstrlen(const char *dstr) {
+	return dstrheader(dstr)->length;
+}
+
+int dstreserve(char **dstr, size_t capacity) {
+	struct dstring *header = dstrheader(*dstr);
+
+	if (capacity > header->capacity) {
+		capacity *= 2;
+
+		header = realloc(header, dstrsize(capacity));
+		if (!header) {
+			return -1;
+		}
+		header->capacity = capacity;
+
+		*dstr = header->data;
+	}
+
+	return 0;
+}
+
+int dstresize(char **dstr, size_t length) {
+	if (dstreserve(dstr, length) != 0) {
+		return -1;
+	}
+
+	struct dstring *header = dstrheader(*dstr);
+	header->length = length;
+	header->data[length] = '\0';
+
+	return 0;
+}
+
+int dstrcat(char **dest, const char *src) {
+	struct dstring *header = dstrheader(*dest);
+	return dstrcatat(dest, header->length, src);
+}
+
+int dstrcatat(char **dest, size_t pos, const char *src) {
+	size_t srclen = strlen(src);
+	size_t destlen = pos + srclen;
+
+	if (dstresize(dest, destlen) != 0) {
+		return -1;
+	}
+
+	memcpy(*dest + pos, src, srclen);
+	return 0;
+}
+
+void dstrfree(char *dstr) {
+	if (dstr) {
+		free(dstrheader(dstr));
+	}
+}