bgrep.c

bgrep.c

// dirty stolen code

#include <unistd.h>
#include <sys/types.h>
#include <dirent.h>
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <stdlib.h>

char* PATTERN = "";
int PATTERN_LEN = 0;

void find_in_file(const char* filename) {
    // Stupid 1 byte at a time
    int fd = open(filename, O_RDONLY);
    if (fd == -1)
        return;
    
    off_t off = lseek(fd, 0, SEEK_END);
    if (off == -1)
        return;

    char* addr = mmap(NULL, off, PROT_READ, MAP_SHARED, fd, 0);

    for (off_t i = 0 ; i < off ; i++) {
        if (addr[i] == PATTERN[0] && (off - i) >= PATTERN_LEN) {
            if (memcmp(&addr[i], PATTERN, PATTERN_LEN) == 0) {
                printf("PATTERN FOUND %s at 0x%lx\n", filename, i);
                munmap(addr, off);
                close(fd);
                return;
            }
        }
    }

    munmap(addr, off);
    close(fd);
}

void listdir(const char *name, int indent)
{
    DIR *dir;
    struct dirent *entry;

    if (!(dir = opendir(name)))
        return;

    while ((entry = readdir(dir)) != NULL) {
        char path[1024];
        snprintf(path, sizeof(path), "%s/%s", name, entry->d_name);
        if (entry->d_type == DT_DIR) {
            if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
                continue;

            // printf("%*s[%s]\n", indent, "", entry->d_name);
            listdir(path, indent + 2);
        } else {
            // printf("%*s- %s\n", indent, "", entry->d_name);
            find_in_file(path);
        }
    }
    closedir(dir);
}

int hexchr2bin(const char hex, char *out)
{
	if (out == NULL)
		return 0;

	if (hex >= '0' && hex <= '9') {
		*out = hex - '0';
	} else if (hex >= 'A' && hex <= 'F') {
		*out = hex - 'A' + 10;
	} else if (hex >= 'a' && hex <= 'f') {
		*out = hex - 'a' + 10;
	} else {
		return 0;
	}

	return 1;
}

size_t hexs2bin(const char *hex, unsigned char **out)
{
	size_t len;
	char   b1;
	char   b2;
	size_t i;

	if (hex == NULL || *hex == '\0' || out == NULL)
		return 0;

	len = strlen(hex);
	if (len % 2 != 0)
		return 0;
	len /= 2;

	*out = (unsigned char*)malloc(len);
	memset(*out, 'A', len);
	for (i=0; i<len; i++) {
		if (!hexchr2bin(hex[i*2], &b1) || !hexchr2bin(hex[i*2+1], &b2)) {
			return 0;
		}
		(*out)[i] = (b1 << 4) | b2;
	}
	return len;
}


int main(int argc, char** argv) {

    if (argc == 2) {
        PATTERN_LEN = hexs2bin(argv[1], (unsigned char **)&PATTERN);
        if (PATTERN_LEN)
            listdir(".", 0);
    }
}