convert stream from https://github.com/easytarget/esp32-cam-webserver to images

strip.c

/*
Copyright (c) <2021> <David Schramm <david.schramm@posteo.de>>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

// cc -Wall -Werror -pedantic -O3 -o strip strip.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define KEY "Content-Length: "
#define NAMEBUF_L 512

int parse_stream(const char *fname, const char *prepend);
void strip(FILE *f, const char *out_n, size_t length);

int main(int ac, char *as[]) {
    if(ac<2) {
        fprintf(stderr, "Usage: %s [file] [?prepend]\n", as[0]);
        return EXIT_FAILURE;
    }
		
	char *inp=strcmp(as[1], "-")==0?NULL:as[1];
    
	return parse_stream(inp, ac>2?as[2]:NULL)?EXIT_FAILURE:EXIT_SUCCESS;
}

inline int seek_to(FILE *f, const char *text, size_t length) {
    char buf[length+1];
    if(fread(buf, sizeof(char), length, f)!=length)
        return 0;
    buf[length]=0;

    for(int c;;) {
        if(strcmp(buf, text)==0)
            return 1;
        if((c=fgetc(f))==-1)
            return 0;
        memcpy(buf, buf+1, length-1);
        buf[length-1]=c;
        buf[length]=0;
    }

}

int parse_stream(const char *fname, const char *prepend) {
    FILE *f=fname==NULL?stdin:fopen(fname,"r");
    if(f==NULL) {
        fprintf(stderr, "could not open \"%s\"!\n", fname);
        return 1;
    }

    const char *pre=prepend==NULL?"out-":prepend;
    char namebuf[NAMEBUF_L];
    size_t clength, num=1, keyl=strlen(KEY);

   	while(!feof(f)) {
        if(!seek_to(f, KEY, keyl))
            break;

        if(fscanf(f, "%lu\r\n\r\n", &clength)==1) {
            //printf("%lu\n", clength);

            snprintf(namebuf, NAMEBUF_L-1, "%s%lu.jpg", pre, num++);
            strip(f, namebuf, clength);
        }
    }

    fclose(f);
    return 0;
}

void strip(FILE *f, const char *out_n, size_t length) {
    FILE *out;
    if((out=fopen(out_n, "w"))==NULL)
        return;

    int c=0;
    for(size_t i=0; i<length; ++i) {
        if((c=fgetc(f))==-1)
            break;
        putc(c, out);
    }

    fclose(out);
}