[FFmpeg-devel] [PATCH] lavu: add stringinterp interface
wm4
nfxjfg at googlemail.com
Sun Dec 8 12:05:00 CET 2013
On Sat, 7 Dec 2013 10:43:17 +0100
Stefano Sabatini <stefasab at gmail.com> wrote:
> From: Clément Bœsch <u at pkh.me>
>
> With very minor changes by Stefano Sabatini.
>
> Based on thread:
> From: Clément Bœsch <ubitux at gmail.com>
> Subject: [FFmpeg-devel] [PATCH] WIP/lavu: add string interpolation helper.
> Date: 2012-02-01 11:01:02 GMT
>
> Signed-off-by: Stefano Sabatini <stefasab at gmail.com>
>
> TODO: bump major, add APIchanges entry, mark as experimental?
> ---
> libavutil/Makefile | 2 +
> libavutil/stringinterp.c | 207 +++++++++++++++++++++++++++++++++++++++++++++++
> libavutil/stringinterp.h | 66 +++++++++++++++
> 3 files changed, 275 insertions(+)
> create mode 100644 libavutil/stringinterp.c
> create mode 100644 libavutil/stringinterp.h
>
> diff --git a/libavutil/Makefile b/libavutil/Makefile
> index 5e0c4ae..c30caae 100644
> --- a/libavutil/Makefile
> +++ b/libavutil/Makefile
> @@ -110,6 +110,7 @@ OBJS = adler32.o \
> samplefmt.o \
> sha.o \
> sha512.o \
> + stringinterp.o \
> time.o \
> timecode.o \
> tree.o \
> @@ -158,6 +159,7 @@ TESTPROGS = adler32 \
> random_seed \
> rational \
> ripemd \
> + stringinterp \
> sha \
> sha512 \
> tree \
> diff --git a/libavutil/stringinterp.c b/libavutil/stringinterp.c
> new file mode 100644
> index 0000000..d1d4fc1
> --- /dev/null
> +++ b/libavutil/stringinterp.c
> @@ -0,0 +1,207 @@
> +/*
> + * Copyright (c) 2012 Clément Bœsch
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +/**
> + * @file
> + * string interpolation
> + */
> +
> +#include "avutil.h"
> +#include "avstring.h"
> +#include "stringinterp.h"
> +
> +struct node {
> + const char *key;
> + const char *value;
> + struct node *next;
> +};
> +
> +typedef struct AVStringInterp {
> + struct node *hashtable[512];
> + char *buf;
> + size_t buf_size;
> +} AVStringInterp;
> +
> +AVStringInterp *av_stringinterp_alloc(void)
> +{
> + AVStringInterp *ctx = av_mallocz(sizeof(*ctx));
> +
> + if (!ctx)
> + return NULL;
> + ctx->buf = av_malloc(128);
> + if (!ctx->buf) {
> + av_free(ctx);
> + return NULL;
> + }
> + ctx->buf_size = 128;
> + return ctx;
> +}
> +
> +void av_stringinterp_free(AVStringInterp **ctx)
> +{
> + int i;
> + AVStringInterp *s = *ctx;
> + for (i = 0; i < FF_ARRAY_ELEMS(s->hashtable); i++) {
> + struct node *tmp, *node = s->hashtable[i];
> + while (node) {
> + tmp = node;
> + node = node->next;
> + av_freep(&tmp);
> + }
> + }
> + av_freep(&s->buf);
> + av_freep(ctx);
> +}
> +
> +static uint32_t get_hash(const char *key, size_t len, int tbl_len)
> +{
> + size_t i;
> + uint32_t hash = 0;
> + for (i = 0; i < len; i++)
> + hash = (hash<<5) ^ (hash>>27) ^ key[i];
> + return hash % tbl_len;
> +}
> +
> +static struct node *create_node(const char *key, const char *value)
> +{
> + struct node *node = av_mallocz(sizeof(*node));
> + if (!node)
> + return NULL;
> + node->key = key;
> + node->value = value;
> + return node;
> +}
> +
> +int av_stringinterp_map(AVStringInterp *ctx, const char *key, const char *value)
> +{
> + uint32_t id = get_hash(key, strlen(key), FF_ARRAY_ELEMS(ctx->hashtable));
> + struct node *node = ctx->hashtable[id];
> + struct node *insert_after = NULL;
> +
> + while (node) {
> + if (!strcmp(key, node->key)) {
> + node->value = value;
> + return 0;
> + }
> + insert_after = node;
> + node = node->next;
> + }
> + node = create_node(key, value);
> + if (!node)
> + return AVERROR(ENOMEM);
> + if (insert_after)
> + insert_after->next = node;
> + else
> + ctx->hashtable[id] = node;
> + return 0;
> +}
> +
> +static const char *get_value(AVStringInterp *ctx, const char *key)
> +{
> + int id;
> + size_t keylen;
> + const char *p = strchr(key, ')');
> + struct node *node;
> +
> + if (!p)
> + return NULL;
> + keylen = p - key;
> + id = get_hash(key, keylen, FF_ARRAY_ELEMS(ctx->hashtable));
> + for (node = ctx->hashtable[id]; node; node = node->next)
> + if (!strncmp(key, node->key, keylen))
> + return node->value;
> + return NULL;
> +}
> +
> +#define APPEND_STRING(str, slen) do { \
> + size_t new_size = pos + slen + 1; \
> + if (new_size > ctx->buf_size) { \
> + char *ptr = av_realloc(ctx->buf, new_size); \
> + if (!ptr) \
> + return NULL; \
> + ctx->buf = ptr; \
> + ctx->buf_size = new_size; \
> + } \
> + av_strlcpy(ctx->buf + pos, str, slen + 1); \
> + pos += slen; \
> +} while (0)
A really evil macro, which doesn't even (quote) its macro parameters.
Why is this a macro, just so you can return from it?
> +char *av_stringinterp_interpolate(AVStringInterp *ctx, const char *s)
> +{
> + const char *p;
> + size_t pos = 0;
> +
> + while (*s) {
> + if (s[0] == '%' && s[1] == '(') {
> + const char *value = get_value(ctx, s + 2);
> + if (value) {
> + APPEND_STRING(value, strlen(value));
> + s = strchr(s, ')') + 1;
> + continue;
> + }
> + }
> + p = strchr(s + 1, '%');
> + if (!p) {
> + APPEND_STRING(s, strlen(s));
> + break;
> + }
> + APPEND_STRING(s, p - s);
> + s = p;
> + }
> + return ctx->buf;
> +}
> +
> +#ifdef TEST
> +
> +static void dump_table(AVStringInterp *ctx)
> +{
> + int i;
> + printf("Hashtable dump:\n");
> + for (i = 0; i < FF_ARRAY_ELEMS(ctx->hashtable); i++) {
> + struct node *node = ctx->hashtable[i];
> + if (!node)
> + continue;
> + printf(" [%02d/%02ld]:", i, FF_ARRAY_ELEMS(ctx->hashtable));
> + while (node) {
> + printf(" \"%s\"=>\"%s\"", node->key, node->value);
> + node = node->next;
> + }
> + printf("\n");
> + }
> +}
> +
> +int main(int ac, char **av)
> +{
> + AVStringInterp *si = av_stringinterp_alloc();
> +
> + av_stringinterp_map(si, "ts1", "0.4123");
> + av_stringinterp_map(si, "ts2", "54.153");
> + av_stringinterp_map(si, "filename", "FooBar");
> + av_stringinterp_map(si, "ext", ".mpg");
> + av_stringinterp_map(si, "ext", ".mp4");
> +
> + dump_table(si);
> +
> + printf("%s\n",
> + av_stringinterp_interpolate(si, "%(filename)_%(ts1)-%(ts2)_%(nokey)%(ext)"));
> + av_stringinterp_free(&si);
> + return 0;
> +}
> +#endif
> diff --git a/libavutil/stringinterp.h b/libavutil/stringinterp.h
> new file mode 100644
> index 0000000..a2331ad
> --- /dev/null
> +++ b/libavutil/stringinterp.h
> @@ -0,0 +1,66 @@
> +/*
> + * Copyright (c) 2012 Clément Bœsch
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +/**
> + * @file
> + * string interpolation header
> + */
> +
> +#ifndef AVUTIL_STRINGINTERP_H
> +#define AVUTIL_STRINGINTERP_H
> +
> +typedef struct AVStringInterp AVStringInterp;
> +
> +/**
> + * Allocate a new string interpolation context.
> + */
> +AVStringInterp *av_stringinterp_alloc(void);
> +
> +/**
> + * Free a AVStringInterp context previously created with
> + * av_stringinterp_alloc().
> + */
> +void av_stringinterp_free(AVStringInterp **ctx);
> +
> +/**
> + * Map a key string with a value string.
> + *
> + * If the key already exists, the value is replaced.
> + * @return 0 in case of success, a negative AVERROR code otherwise
> + * @note key and value are not duplicated, you must keep a reference
> + * to them.
> + */
> +int av_stringinterp_map(AVStringInterp *ctx, const char *key, const char *value);
> +
> +/**
> + * Do the string interpolation.
> + *
> + * The value to interpolate must have the form "%(key)", where key is
> + * the name to be changed with the value previously stored in the
> + * AVStringInterp structure. In case the key is not recognized, it is
> + * ignored.
> + *
> + * @return a pointer to the printable string, or NULL in case of failure
> + * @note The returned buffer is kept in the AVStringInterp context, you must
> + * not free it.
> + */
> +char *av_stringinterp_interpolate(AVStringInterp *ctx, const char *s);
> +
> +#endif/* AVUTIL_STRINGINTERP_H */
Is there a reason why this is so complex, including hashtables etc.? It
could be a single function that takes a string list (even a statically
allocated one).
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