gdb-server/response.c

#include <response.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>

static bool write_char(RdbResponse *res, char out)  {
    if (res->len >= res->buflen) {
        return false;
    }
    if (out == '#' || out == '$' || out == '}' || out == '*') {
        res->buf[res->len++] = '}';
        res->chk += '}';
        if (res->len >= res->buflen) {
            return false;
        }
        out ^= 0x20;
    }
    res->buf[res->len++] = out;
    res->chk += out;
    return true;
}

bool char_to_hex_digit(char in, char *out) {
    if (in & 0xf0) {
        return false;
    }
    in &= 0x0f;
    if (in > 9) {
        *out = 'a' + in - 10;
    } else {
        *out = '0' + in;
    }
    return true;
}

bool char_to_hex_digits(char in, char *hi, char *lo) {
    return char_to_hex_digit((in & 0xf0) >> 4, hi)
        && char_to_hex_digit(in & 0x0f, lo);
}

void rdb_response_init(RdbResponse *res, int connfd, char *buf, size_t buflen) {
    res->connfd = connfd;
    res->buf = buf;
    res->buflen = buflen;
    res->len = 0;
    res->chk = 0;
    res->should_ack = true;
}

void rdb_response_begin_packet(RdbResponse *res) {
    res->len = 0;
    res->chk = 0;
    if (res->should_ack) {
        res->buf[res->len++] = '+';
    }
    res->buf[res->len++] = '$';
}

bool rdb_response_write_str(RdbResponse *res, const char *str) {
    size_t len = strlen(str);
    for (size_t i = 0; i < len; ++i) {
        if (!write_char(res, str[i])) {
            return false;
        }
    }
    return true;
}

bool rdb_response_write_str_hex(RdbResponse *res, const char *str) {
    size_t len = strlen(str);
    for (size_t i = 0; i < len; ++i) {
        char hi, lo;
        if (!char_to_hex_digits(str[i], &hi, &lo)
            || !write_char(res, hi)
            || !write_char(res, lo)) {
                return false;
        }
    }
    return true;
}

bool rdb_response_write_i8_hex(RdbResponse *res, uint8_t value) {
    char hi, lo;
    return char_to_hex_digits(value, &hi, &lo)
        && write_char(res, hi)
        && write_char(res, lo);
}

bool rdb_response_write_i32_hex(RdbResponse *res, uint32_t value) {
    return rdb_response_write_i8_hex(res, (uint8_t) value)
        && rdb_response_write_i8_hex(res, (uint8_t) (value >> 8))
        && rdb_response_write_i8_hex(res, (uint8_t) (value >> 16))
        && rdb_response_write_i8_hex(res, (uint8_t) (value >> 24));
}

int rdb_response_send_packet(RdbResponse *res) {
    if (res->len + 3 > res->buflen) {
        return -1;
    }
    res->buf[res->len++] = '#';
    char hi, lo;
    if (!char_to_hex_digits(res->chk, &hi, &lo)) {
        return -1;
    }
    res->buf[res->len++] = hi;
    res->buf[res->len++] = lo;
    printf("sending command \"%.*s\" %d\n", (int) res->len, res->buf, (int)res->len);

    ssize_t rwrite = write(res->connfd, res->buf, res->len);
    if (rwrite == -1) {
        return -1;
    }
    return 0;
}