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// Copyright © Tavian Barnes <tavianator@tavianator.com>
// SPDX-License-Identifier: 0BSD
#include "dstring.h"
#include <assert.h>
#include <stdarg.h>
#include <stdio.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[];
};
/** Get the string header from the string data pointer. */
static struct dstring *dstrheader(const char *dstr) {
return (struct dstring *)(dstr - offsetof(struct dstring, data));
}
/** Get the correct size for a dstring with the given capacity. */
static size_t dstrsize(size_t capacity) {
return flex_sizeof(struct dstring, data, capacity + 1);
}
/** Allocate a dstring with the given contents. */
static char *dstralloc_impl(size_t capacity, size_t length, const char *data) {
// Avoid reallocations for small strings
if (capacity < 7) {
capacity = 7;
}
struct dstring *header = malloc(dstrsize(capacity));
if (!header) {
return NULL;
}
header->capacity = capacity;
header->length = length;
memcpy(header->data, data, length);
header->data[length] = '\0';
return header->data;
}
char *dstralloc(size_t capacity) {
return dstralloc_impl(capacity, 0, "");
}
char *dstrdup(const char *str) {
size_t len = strlen(str);
return dstralloc_impl(len, len, str);
}
char *dstrndup(const char *str, size_t n) {
size_t len = strnlen(str, n);
return dstralloc_impl(len, len, str);
}
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;
}
/** Common implementation of dstr{cat,ncat,app}. */
static int dstrcat_impl(char **dest, const char *src, size_t srclen) {
size_t oldlen = dstrlen(*dest);
size_t newlen = oldlen + srclen;
if (dstresize(dest, newlen) != 0) {
return -1;
}
memcpy(*dest + oldlen, src, srclen);
return 0;
}
int dstrcat(char **dest, const char *src) {
return dstrcat_impl(dest, src, strlen(src));
}
int dstrncat(char **dest, const char *src, size_t n) {
return dstrcat_impl(dest, src, strnlen(src, n));
}
int dstrdcat(char **dest, const char *src) {
return dstrcat_impl(dest, src, dstrlen(src));
}
int dstrapp(char **str, char c) {
return dstrcat_impl(str, &c, 1);
}
char *dstrprintf(const char *format, ...) {
va_list args;
va_start(args, format);
char *str = dstrvprintf(format, args);
va_end(args);
return str;
}
char *dstrvprintf(const char *format, va_list args) {
// Guess a capacity to try to avoid reallocating
char *str = dstralloc(2*strlen(format));
if (!str) {
return NULL;
}
if (dstrvcatf(&str, format, args) != 0) {
dstrfree(str);
return NULL;
}
return str;
}
int dstrcatf(char **str, const char *format, ...) {
va_list args;
va_start(args, format);
int ret = dstrvcatf(str, format, args);
va_end(args);
return ret;
}
int dstrvcatf(char **str, const char *format, va_list args) {
// Guess a capacity to try to avoid calling vsnprintf() twice
size_t len = dstrlen(*str);
dstreserve(str, len + 2*strlen(format));
size_t cap = dstrheader(*str)->capacity;
va_list copy;
va_copy(copy, args);
char *tail = *str + len;
int ret = vsnprintf(tail, cap - len + 1, format, args);
if (ret < 0) {
goto fail;
}
size_t tail_len = ret;
if (tail_len > cap - len) {
cap = len + tail_len;
if (dstreserve(str, cap) != 0) {
goto fail;
}
tail = *str + len;
ret = vsnprintf(tail, tail_len + 1, format, copy);
if (ret < 0 || (size_t)ret != tail_len) {
assert(!"Length of formatted string changed");
goto fail;
}
}
va_end(copy);
struct dstring *header = dstrheader(*str);
header->length += tail_len;
return 0;
fail:
*tail = '\0';
return -1;
}
void dstrfree(char *dstr) {
if (dstr) {
free(dstrheader(dstr));
}
}
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