在C中输出文本块

我有一个很大的字符数组 data strncpy 就这么多。然而,当我去打印出来,我没有输出。一定有点小问题,但我看不出是怎么回事。

char* data;
int blocks[100], block_sizes[100];
int traversed, block_idx, nl_chars, i, len, chars;
char* block;

// Determine output blocks
nl_chars = 0;
block_idx = 1;
blocks[0] = 0;
chars = 0;
len = strlen(data);
for (i = 0; i < len; i++) {
    chars++;
    if (data[i] == '\n') {
        nl_chars++;
    }

    if (data[i] == '\0' || nl_chars == 30) {
        blocks[block_idx] = i;
        block_sizes[block_idx - 1] = chars;
        block_idx++;
        nl_chars = 0;
        chars = 0;
    }
}

// Output blocks to stdout
traversed = 0;
while (traversed < block_idx) {
    block = malloc(block_sizes[traversed] * sizeof(char));
    if (block == NULL) {
        error("[-]Unable to allocate required memory");
    }
    strncpy(block, data + blocks[traversed], block_sizes[traversed]);
    printf("%s", block);
    free(block);

    while (1) {
        memset(input, 0, BUFFER_SIZE);
        fgets(input, sizeof(input), stdin);
        fflush(stdin);
        if (input[0] == '\n' || input[0] == '\r') {
            break;
        }
    }

    traversed++;
}