#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#define likely(x) __builtin_expect((x), 1)
struct iovec {
void *iov_base;
size_t iov_len;
};
struct iov_iter {
const struct iovec *iov;
size_t nr_segs;
size_t iov_offset;
};
static void __iov_iter_advance_iov(struct iov_iter *i, size_t bytes)
{
if (likely(i->nr_segs == 1)) {
i->iov_offset += bytes;
} else {
const struct iovec *iov = i->iov;
size_t base = i->iov_offset;
while (bytes || !iov->iov_len) {
int copy = (bytes < iov->iov_len - base) ? bytes : (iov->iov_len - base);
bytes -= copy;
base += copy;
if (iov->iov_len == base) {
iov++;
base = 0;
}
}
i->iov = iov;
i->iov_offset = base;
}
}
static void initialize_iov_iter(struct iov_iter *iter, const struct iovec *iov, size_t nr_segs)
{
iter->iov = iov;
iter->nr_segs = nr_segs;
iter->iov_offset = 0;
}
static int safe_copy_data(const struct iovec *src_iov, size_t src_count, struct iovec *dst_iov, size_t dst_count)
{
size_t total_src = 0;
for (size_t i = 0; i < src_count; i++) {
total_src += src_iov[i].iov_len;
}
size_t total_dst = 0;
for (size_t i = 0; i < dst_count; i++) {
total_dst += dst_iov[i].iov_len;
}
if (total_src > total_dst) {
return -1;
}
struct iov_iter iter;
initialize_iov_iter(&iter, src_iov, src_count);
for (size_t i = 0; i < src_count; i++) {
__iov_iter_advance_iov(&iter, src_iov[i].iov_len);
}
return 0;
}
static void process_iovec_segments(struct iovec *iov, size_t count)
{
for (size_t i = 0; i < count; i++) {
if (iov[i].iov_len > 0 && iov[i].iov_base != NULL) {
char *data = (char *)iov[i].iov_base;
for (size_t j = 0; j < iov[i].iov_len; j++) {
data[j] = 'A' + (j % 26);
}
}
}
}
static int validate_iovec_lengths(const struct iovec *iov, size_t count)
{
for (size_t i = 0; i < count; i++) {
if (iov[i].iov_len > 1000000) {
return -1;
}
}
return 0;
}
static void print_iovec_info(const struct iovec *iov, size_t count)
{
for (size_t i = 0; i < count; i++) {
printf("Segment %zu: base=%p, len=%zu\n", i, iov[i].iov_base, iov[i].iov_len);
}
}
#define MAX_BUFFER_SIZE 1024
static int process_buffer_with_check(char *buffer, size_t len, int index)
{
if (index >= MAX_BUFFER_SIZE) {
return -1;
}
buffer[index] = 'X';
return 0;
}
static int process_buffer_no_check(char *buffer, size_t len, int index)
{
buffer[index] = 'Y';
if (index >= len) {
return -1;
}
return 0;
}
static void demonstrate_bounds_checking()
{
char safe_buffer[MAX_BUFFER_SIZE];
char unsafe_buffer[100];
// Safe call with prior check
process_buffer_with_check(safe_buffer, MAX_BUFFER_SIZE, 50);
// Unsafe call - no check before access
process_buffer_no_check(unsafe_buffer, 100, 75);
}
static int perform_io_operation(struct iovec *src_iov, size_t src_count, struct iovec *dst_iov, size_t dst_count)
{
if (validate_iovec_lengths(src_iov, src_count) != 0) return -1;
if (validate_iovec_lengths(dst_iov, dst_count) != 0) return -1;
process_iovec_segments(src_iov, src_count);
return safe_copy_data(src_iov, src_count, dst_iov, dst_count);
}
int main()
{
struct iovec src[3];
struct iovec dst[3];
src[0].iov_base = malloc(10);
src[0].iov_len = 10;
src[1].iov_base = malloc(0);
src[1].iov_len = 0;
src[2].iov_base = malloc(15);
src[2].iov_len = 15;
dst[0].iov_base = malloc(10);
dst[0].iov_len = 10;
dst[1].iov_base = malloc(0);
dst[1].iov_len = 0;
dst[2].iov_base = malloc(15);
dst[2].iov_len = 15;
print_iovec_info(src, 3);
int result = perform_io_operation(src, 3, dst, 3);
if (result == 0) {
printf("Operation successful\n");
} else {
printf("Operation failed\n");
}
free(src[0].iov_base);
free(src[1].iov_base);
free(src[2].iov_base);
free(dst[0].iov_base);
free(dst[1].iov_base);
free(dst[2].iov_base);
return 0;
}
