129 lines
3.2 KiB
C
129 lines
3.2 KiB
C
#define _POSIX_C_SOURCE 200809L
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#include <sys/types.h>
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#include <err.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <inttypes.h>
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#include <limits.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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static uint64_t
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parse_number(const char *text, const char *what)
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{
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char *end;
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uintmax_t value;
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errno = 0;
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value = strtoumax(text, &end, 0);
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if (errno != 0 || *text == '\0' || *end != '\0' || value > INT64_MAX)
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errx(2, "invalid %s: %s", what, text);
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return ((uint64_t)value);
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}
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static void
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write_all(int fd, const unsigned char *buffer, size_t length)
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{
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size_t done;
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ssize_t written;
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for (done = 0; done < length; done += (size_t)written) {
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written = write(fd, buffer + done, length - done);
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if (written < 0)
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err(1, "write output");
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}
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}
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static void
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pread_range(const char *path, uint64_t raw_offset, uint64_t raw_length,
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const char *output)
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{
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unsigned char buffer[65536];
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uint64_t done;
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ssize_t count;
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size_t request;
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int fd, outfd;
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if (raw_length > INT64_MAX - raw_offset)
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errx(2, "offset plus length overflows off_t");
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fd = open(path, O_RDONLY);
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if (fd < 0)
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err(1, "open %s", path);
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outfd = open(output, O_WRONLY | O_CREAT | O_TRUNC, 0600);
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if (outfd < 0)
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err(1, "open %s", output);
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for (done = 0; done < raw_length; done += (uint64_t)count) {
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request = raw_length - done < sizeof(buffer) ?
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(size_t)(raw_length - done) : sizeof(buffer);
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count = pread(fd, buffer, request, (off_t)(raw_offset + done));
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if (count < 0)
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err(1, "pread %s at %ju", path,
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(uintmax_t)(raw_offset + done));
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if (count == 0)
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errx(1, "unexpected EOF at %ju", (uintmax_t)(raw_offset + done));
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write_all(outfd, buffer, (size_t)count);
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}
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if (close(outfd) != 0 || close(fd) != 0)
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err(1, "close");
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printf("bytes=%ju offset=%ju\n", (uintmax_t)raw_length,
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(uintmax_t)raw_offset);
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}
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static void
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expect_error(const char *path, int expected)
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{
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unsigned char buffer[65536];
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ssize_t count;
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int fd;
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fd = open(path, O_RDONLY);
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if (fd < 0) {
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if (errno != expected)
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errx(1, "open returned %s, expected errno %d",
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strerror(errno), expected);
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printf("expected_errno=%d stage=open\n", expected);
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return;
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}
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for (;;) {
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errno = 0;
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count = read(fd, buffer, sizeof(buffer));
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if (count < 0)
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break;
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if (count == 0)
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errx(1, "read reached EOF without expected errno %d", expected);
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}
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if (errno != expected)
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errx(1, "read returned %s, expected errno %d",
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strerror(errno), expected);
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if (close(fd) != 0)
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err(1, "close");
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printf("expected_errno=%d stage=read\n", expected);
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}
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int
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main(int argc, char **argv)
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{
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uint64_t offset, length, error_number;
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if (argc == 6 && strcmp(argv[1], "pread") == 0) {
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offset = parse_number(argv[3], "offset");
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length = parse_number(argv[4], "length");
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pread_range(argv[2], offset, length, argv[5]);
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return (0);
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}
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if (argc == 4 && strcmp(argv[1], "expect-error") == 0) {
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error_number = parse_number(argv[3], "errno");
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if (error_number == 0 || error_number > INT_MAX)
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errx(2, "errno is out of range");
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expect_error(argv[2], (int)error_number);
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return (0);
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}
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errx(2, "usage: %s pread FILE OFFSET LENGTH OUTPUT | "
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"expect-error FILE ERRNO", argv[0]);
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}
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