Mutex for threading

mutthread.c

#include <pthread.h>
#include <stdlib.h>
#include <string.h>

typedef struct {
    char *data;
    size_t size;
    size_t capacity;
    pthread_mutex_t lock;
} Buffer;

void buffer_init(Buffer *buf, size_t initial_capacity) {
    buf->data = malloc(initial_capacity);
    buf->size = 0;
    buf->capacity = initial_capacity;
    pthread_mutex_init(&buf->lock, NULL);
}

void buffer_write(Buffer *buf, const char *input, size_t len) {
    pthread_mutex_lock(&buf->lock);

    if (buf->size + len > buf->capacity) {
        size_t new_capacity = buf->capacity * 2 + len;
        char *new_data = realloc(buf->data, new_capacity);
        if (new_data) {
            buf->data = new_data;
            buf->capacity = new_capacity;
        } else {
            // handle allocation failure
            pthread_mutex_unlock(&buf->lock);
            return;
        }
    }

    memcpy(buf->data + buf->size, input, len);
    buf->size += len;

    pthread_mutex_unlock(&buf->lock);
}