From 99e5d81ef997cb88b1a40e6f253f37f7cbf251d9 Mon Sep 17 00:00:00 2001 From: Steven Liu Date: Sat, 1 Apr 2017 10:55:04 +0800 Subject: [PATCH] avutil/avstring: add av_strreplace API into avstring refer to: http://creativeandcritical.net/str-replace-c add av_strreplace API for replace string operations. Signed-off-by: Steven Liu --- libavutil/avstring.c | 77 ++++++++++++++++++++++++++++++++++++++++++++ libavutil/avstring.h | 5 +++ 2 files changed, 82 insertions(+) diff --git a/libavutil/avstring.c b/libavutil/avstring.c index 1787a1ef54..52e6e6cd13 100644 --- a/libavutil/avstring.c +++ b/libavutil/avstring.c @@ -231,6 +231,83 @@ int av_strncasecmp(const char *a, const char *b, size_t n) return c1 - c2; } +char *av_strreplace(const char *str, const char *from, const char *to) +{ + /* Adjust each of the below values to suit your needs. */ + /* Increment positions cache size initially by this number. */ + size_t cache_sz_inc = 16; + /* Thereafter, each time capacity needs to be increased, + * multiply the increment by this factor. */ + const size_t cache_sz_inc_factor = 3; + /* But never increment capacity by more than this number. */ + const size_t cache_sz_inc_max = 1048576; + + char *pret, *ret = NULL; + const char *pstr2, *pstr = str; + size_t i, count = 0; + uintptr_t *pos_cache_tmp, *pos_cache = NULL; + size_t cache_sz = 0; + size_t cpylen, orglen, retlen, tolen, fromlen = strlen(from); + + /* Find all matches and cache their positions. */ + while ((pstr2 = av_stristr(pstr, from))) { + count++; + /* Increase the cache size when necessary. */ + if (cache_sz < count) { + cache_sz += cache_sz_inc; + pos_cache_tmp = av_realloc(pos_cache, sizeof(*pos_cache) * cache_sz); + if (!pos_cache_tmp) { + goto end_strreplace; + } else pos_cache = pos_cache_tmp; + cache_sz_inc *= cache_sz_inc_factor; + if (cache_sz_inc > cache_sz_inc_max) { + cache_sz_inc = cache_sz_inc_max; + } + } + + pos_cache[count-1] = pstr2 - str; + pstr = pstr2 + fromlen; + } + orglen = pstr - str + strlen(pstr); + /* Allocate memory for the post-replacement string. */ + if (count > 0) { + tolen = strlen(to); + retlen = orglen + (tolen - fromlen) * count; + } else { + retlen = orglen; + } + ret = av_malloc(retlen + 1); + if (!ret) { + goto end_strreplace; + } + + if (!count) { + /* If no matches, then just duplicate the string. */ + av_strlcpy(ret, str, retlen + 1); + } else { + /* Otherwise, duplicate the string whilst performing + * the replacements using the position cache. */ + pret = ret; + memcpy(pret, str, pos_cache[0]); + pret += pos_cache[0]; + for (i = 0; i < count; i++) { + memcpy(pret, to, tolen); + pret += tolen; + pstr = str + pos_cache[i] + fromlen; + cpylen = (i == count-1 ? orglen : pos_cache[i+1]) - pos_cache[i] - fromlen; + memcpy(pret, pstr, cpylen); + pret += cpylen; + } + ret[retlen] = '\0'; + } + +end_strreplace: + /* Free the cache and return the post-replacement string, + * which will be NULL in the event of an error. */ + av_free(pos_cache); + return ret; +} + const char *av_basename(const char *path) { char *p = strrchr(path, '/'); diff --git a/libavutil/avstring.h b/libavutil/avstring.h index dd2876990f..33be8bf484 100644 --- a/libavutil/avstring.h +++ b/libavutil/avstring.h @@ -266,6 +266,11 @@ int av_strcasecmp(const char *a, const char *b); */ int av_strncasecmp(const char *a, const char *b, size_t n); +/** + * Locale-independent strings replace. + * @note This means only ASCII-range characters are replace + */ +char *av_strreplace(const char *str, const char *from, const char *to); /** * Thread safe basename.