Take a PGCOPY binary in via stdin and output via stdout

pgcat.c

#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <stdbool.h>
#include <arpa/inet.h>

typedef struct buffer
{
    uint32_t length;
    uint32_t capacity;
    char* data;
} buffer_t;

int
main(void)
{
    {
        uint8_t skip[19];
        if (fread(skip, 19, 1, stdin) != 1) {
            fprintf(stderr, "failed to read the skip\n");
            return EXIT_FAILURE;
        }
    }

    buffer_t buffer;
    buffer.length   = 0;
    buffer.capacity = 4096;
    buffer.data     = calloc(1, 4096 + 1);

    while (true) {
        uint16_t count;
        uint32_t bytes;

        if (fread(&count, sizeof(uint16_t), 1, stdin) != 1) {
            fprintf(stderr, "failed to read tuple's field count\n");
            return EXIT_FAILURE;
        }

        if (count == 0xffff) {
            free(buffer.data);
            return EXIT_SUCCESS;
        }

        if (fread(&bytes, sizeof(uint32_t), 1, stdin) != 1) {
            fprintf(stderr, "failed to read tuple's field bytes\n");
            return EXIT_FAILURE;
        }

        count = ntohs(count);
        bytes = ntohl(bytes);

        if (buffer.capacity < bytes) {
            free(buffer.data);
            buffer.data = calloc(1, bytes + 1);
            buffer.capacity = bytes + 1;
        }

        if (fread(buffer.data, 1, bytes, stdin) != bytes) {
            fprintf(stderr, "failed to read in row data\n");
            return EXIT_FAILURE;
        }
        buffer.length = bytes;
        buffer.data[bytes] = '\0';

        fprintf(stdout, "%s\n", buffer.data);
    }

    free(buffer.data);

    return EXIT_SUCCESS;
}