getline.c

#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>

const size_t BUFFERGROWTH = 128;

size_t getline_(char **lineptr, size_t *linesize, FILE *stream)
{
    if (*lineptr == NULL) {
        *lineptr = malloc(BUFFERGROWTH);
        *linesize = BUFFERGROWTH;
    }
    size_t buffer_i = 0;
    char c = 0;
    while (c != '\n') {
        // Detect need for buffer growth
        if (buffer_i >= *linesize) {
            *linesize += BUFFERGROWTH;
            *lineptr = realloc(*lineptr, *linesize);
        }
        c = getc(stream);
        if (c == -1) { // EOF
            break;
        }
        (*lineptr)[buffer_i++] = c;
    }
    (*lineptr)[buffer_i] = '\0';
    return buffer_i;
}