Simple buffer library

.gitignore

main
*.o

buffer.c

#include "buffer.h"

Buffer *
buffer_alloc(int initial_size)
{
    Buffer *buf     = malloc(sizeof(Buffer));
    buf->contents   = calloc(1, initial_size * sizeof(char));
    buf->bytes_used = 0;
    buf->total_size = initial_size;

    return buf;
}

void
buffer_free(Buffer *buf)
{
    free(buf->contents);
    free(buf);
}

int
buffer_has_space(Buffer *buf, int desired_length)
{
    return desired_length <= (buf->total_size - buf->bytes_used - 1);
}

int
buffer_grow(Buffer *buf, int minimum_size)
{
    int min_allocation = minimum_size + 1; // Need to hold NUL
    int new_size       = (buf->total_size * 2);

    if (new_size < min_allocation) {
        new_size = min_allocation;
    }

    char *tmp = realloc(buf->contents, new_size * sizeof(char));
    if (tmp == NULL) { return -1; }

    buf->contents   = tmp;
    buf->total_size = new_size;

    return 0;
}

void
buffer_cat(Buffer *buf, char *append, int length)
{
    int i               = 0;
    int bytes_copied    = 0;
    int buffer_position = 0;

    for (i = 0; i < length; i++) {
        if (append[i] == '\0') { break; }
        
        buffer_position = buf->bytes_used + i;
        *(buf->contents + buffer_position) = append[i];
        
        bytes_copied++;
    }

    buf->bytes_used += bytes_copied;
    *(buf->contents + buf->bytes_used) = '\0';
}

int
buffer_append(Buffer *buf, char *append, int length)
{
    int status = 0;

    if (!buffer_has_space(buf, length)) {
        status = buffer_grow(buf, length);
        if (status == -1) { return -1; }
    }

    buffer_cat(buf, append, length);

    return 0;
}

buffer.h

#ifndef BUFFER_H
#define BUFFER_H

#include <stdlib.h>
#include <strings.h>

struct Buffer {
    char *contents;
    int bytes_used;
    int total_size;
};

typedef struct Buffer Buffer;

Buffer * buffer_alloc(int initial_size);
void buffer_free(Buffer *str);
int buffer_append(Buffer *str, char *append, int length);

#endif

main.c

#include <stdlib.h>
#include <stdio.h>
#include "buffer.h"

void
print_chars(Buffer *buf)
{
    int i = 0;
    char ch;

    for(i = 0; i < buf->total_size; i++) {
        printf("%d", (i + 1) % 10);
    }
    printf("\n");

    for(i = 0; i < buf->total_size; i++) {
        ch = *(buf->contents + i);

        if (ch == '\0') {
            printf("N");
        } else {
            printf("%c", ch);
        }
    }
    printf("\n");
}

int
main(int argc, const char *argv[])
{
    int i = 0;

    Buffer *buf = buffer_alloc(8);
    char *content = "123456";

    for (i = 0; i < 20; i++) {
        buffer_append(buf, content, 6);
        printf("`buf`: %s\n", buf->contents);
    }

    buffer_free(buf);

    return 0;
}

Makefile

CFLAGS=-Wall -g

all: main

main: main.o buffer.o

clean:
	rm -rf main *.o *.dSYM