dpkg-delta.c

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

struct tar_header {
    char name[100];
    char mode[8];
    char uid[8];
    char gid[8];
    char size[12];
    char mtime[12];
    char checksum[8];
    char linkflag;
    char linkname[100];

    /* Only valid on ustar and gnu. */
    char magic[8];
    char user[32];
    char group[32];
    char devmajor[8];
    char devminor[8];

    /* Only valid on ustar. */
    char prefix[155];
};

void skip(FILE *input, long size)
{
    char buf[32*1024];
    while (size > 0) {
        long skip = 4096;
        if (skip > size)
            skip = size;

        if (fread(buf, skip, 1, input) < 0)
            perror("fread");

        size -= skip;
    }
}

//#define setvbuf(...) (void)0

typedef struct {
    int bar[sizeof(struct tar_header) <= 512 ? 1 : -1];
} foo;

int main(int argc, char *argv[])
{
    union {
        struct tar_header t;
        char buf[512];
    } header;
    char pathbuf[4096];

    FILE *input = fopen(argv[3], "rb");

            setvbuf(input, 0, _IONBF,0);

    while (fread(&header, sizeof(header), 1, input)) {

        char buf[13];
        buf[12] = 0;
        
        memcpy(buf, header.t.size, sizeof(header.t.size));

        long long size = strtoll(buf, NULL, 8);
        long long toskip = strtoll(buf, NULL, 8);
        long long toskip512 = toskip;

        while (toskip512 % 512 != 0)
            toskip512++;

        //printf("Found: %.100s with size %.12s %lld\n", header.t.name, header.t.size, strtoll(buf, NULL, 8));
        if (strlen(header.t.name) > 7
            && memcmp(header.t.name + strlen(header.t.name) - 7, ".jkdiff",
                      7) == 0) {
            header.t.name[strlen(header.t.name) - 7] = 0;

            //fprintf(stderr, "%s\n", header.t.name);
        
        #if 1


            sprintf(pathbuf, "%s/%s", argv[1], header.t.name);

            FILE *old = fopen(pathbuf, "rb");
            if (old == NULL)
                return perror(pathbuf), 1;

            sprintf(pathbuf, "%s/%s", argv[2], header.t.name);
            FILE *new = fopen(pathbuf, "wb");
            if (new == NULL)
                return perror(pathbuf), 1;



#if 0
            int fd = limit_fd(fileno(input), size);
            if (fd == -1)
                return perror("limit input"), 1;
            FILE *patch = fdopen(fd, "rb");
            if (patch == NULL)
                return perror("limit input"), 1;
#else
            FILE *patch = input;
#endif

            if (jkpatch(patch, old, new) != 0) {
                fprintf(stderr, "Error patching %s", header.t.name);
            }

            fclose(old);
            fclose(new);


            toskip512 -= toskip;
        }
        #endif

        skip(input, toskip512);
    }

}