Nils O. Selåsdal
96 lines
2.0 KiB
C
96 lines
2.0 KiB
C
#include <stdlib.h>
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#include <limits.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include "ucore/read_file.h"
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#define CHUNK_SZ 1024
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char *
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uc_read_fd(int fd, size_t *length, size_t max)
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{
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char *s = NULL;
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char *p;
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struct stat statb;
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size_t alloc_sz;
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*length = 0;
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if (fstat(fd, &statb) == -1) {
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goto out_close;
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}
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if ((statb.st_mode & S_IFMT) == S_IFREG) {
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if (statb.st_size > (off_t)max) {
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errno = EMSGSIZE;
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goto out_close;
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}
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if (statb.st_size > SSIZE_MAX) {
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//otherwise we cannot detect the return value of read()
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alloc_sz = SSIZE_MAX;
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} else {
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alloc_sz = statb.st_size;
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}
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} else {
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alloc_sz = CHUNK_SZ;
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}
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s = malloc(alloc_sz + 1); //+1 for nul terminator
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if (s == NULL) {
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goto out_close;
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}
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p = s;
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for (;;) {
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ssize_t rc = read(fd, p, alloc_sz - (p - s));
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if (rc == 0) {
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*p = 0; // nul terminate. all malloc calls adds room for this byte
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goto out_close;
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} else if (rc == -1) {
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goto out_err_free;
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} else if (*length + rc > max) {
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errno = EMSGSIZE;
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goto out_err_free;
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}
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if (p + rc == s + alloc_sz) { //reached end of allocated memory, grow it.
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char *tmp = realloc(s, alloc_sz + CHUNK_SZ + 1);
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if (tmp == NULL) {
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goto out_err_free;
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}
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s = tmp;
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p = s + alloc_sz;
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alloc_sz += CHUNK_SZ;
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} else {
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p += rc;
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}
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*length += rc;
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}
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out_err_free:
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free(s);
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s = NULL;
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out_close:
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close(fd);
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return s;
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}
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char *
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uc_read_file(const char *f, size_t *length, size_t max)
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{
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int fd;
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if ((fd = open(f, O_RDONLY)) == -1) {
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*length = 0;
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return NULL;
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}
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return uc_read_fd(fd, length, max);
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}
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