diff options
| -rw-r--r-- | src/common.h | 39 | ||||
| -rw-r--r-- | src/send.c | 256 |
2 files changed, 214 insertions, 81 deletions
diff --git a/src/common.h b/src/common.h new file mode 100644 index 0000000..c7ec189 --- /dev/null +++ b/src/common.h @@ -0,0 +1,39 @@ +/** + * Copyright © 2015 Mattias Andrée (maandree@member.fsf.org) + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + */ + + +/** + * Byte used to escape bytes with special interpretation. + * + * This is the 'Data link escape' character. + */ +#define CHAR_ESCAPE 0x10 + +/** + * Byte used to mark a transmission as aborted (abnormal termination.) + * + * This is the 'Cancel' character. + */ +#define CHAR_CANCEL 0x18 + +/** + * Byte used to mark the end of a transmission (normal termination.) + * + * This is the 'End of transmission' character. + */ +#define CHAR_END 0x04 + @@ -14,10 +14,14 @@ * You should have received a copy of the GNU General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. */ +#include "common.h" + #include <stdio.h> #include <math.h> /* -lm */ #include <stdint.h> #include <alsa/asoundlib.h> /* dep: alsa-lib (pkg-config alsa) */ +#include <signal.h> + #define UTYPE uint32_t @@ -29,165 +33,255 @@ #define DURATION 100 /* ms */ /* 100 ms → 10 Bd → 5 B/s */ #define LATENCY 100000 /* µs */ -#define CHAR_ESCAPE 0x10 /* Data link escape */ -#define CHAR_CANCEL 0x18 /* Cancel */ -#define CHAR_END 0x04 /* End of transmission */ -#define N(buf) (sizeof(buf) / sizeof(*buf)) +/** + * Name number of samples per tone. + */ +#define N SAMPLE_RATE / 1000 * DURATION + +/** + * The process's name. + */ static const char* argv0; + +/** + * Audio descriptor. + */ static snd_pcm_t* sound_handle = NULL; +/** + * Audio playback buffer for each nibble. + */ +static UTYPE buffers[16][N]; + -void get_freq(int nibble, int* low, int* high) + +/** + * Use to accept signals, without doing anything + * about them, just be interrupted. + * + * @param signo The received signal. + */ +static void signoop(int signo) { - static const int LOW[] = { 697, 770, 852, 941 }; + (void) signo; +} + + +/** + * Get the tones used to transmit a nibble. + * + * @param nibble The nibble. + * @param low Output parameter for the lower frequency. + * @param high Output parameter for the higher frequency. + */ +static void get_freq(int nibble, int* low, int* high) +{ + static const int LOW[] = { 697, 770, 852, 941 }; static const int HIGH[] = { 1209, 1336, 1477, 1663 }; *low = LOW[(nibble >> 0) & 0x03]; *high = HIGH[(nibble >> 2) & 0x03]; } -int send_tones(int low, int high) + +/** + * Initialise to before for each nibble. + */ +static void init_buffers(void) { -#define GENERATE_TONE(tone) \ - sin(2 * M_PI * ((double)i / (SAMPLE_RATE / (tone)))) +#define GENERATE_TONE(tone) sin(2 * M_PI * ((double)i / (SAMPLE_RATE / (tone)))) - static UTYPE buffer[SAMPLE_RATE / 1000 * DURATION]; - snd_pcm_sframes_t frames; - int r; size_t i; + UTYPE* buffer; + int j, low, high; - for (i = 0; i < N(buffer); i++) - buffer[i] = (GENERATE_TONE(low * 1) + GENERATE_TONE(high * 1) + - GENERATE_TONE(low * 4) + GENERATE_TONE(high * 4)) * - (SMAX / 4) - SMIN; + for (j = 0; j < 16; j++) + { + buffer = buffers[j]; + get_freq(j, &low, &high); + + for (i = 0; i < N; i++) + buffer[i] = (GENERATE_TONE(low * 1) + GENERATE_TONE(high * 1) + + GENERATE_TONE(low * 4) + GENERATE_TONE(high * 4)) * + (SMAX / 4) - SMIN; + } +} + + +/** + * Transmit a nibble. + * + * @param n The nibble. + * @return 0 on success, -1 on error. + */ +static int send_nibble(int n) +{ + UTYPE* buffer = buffers[n]; + snd_pcm_sframes_t frames; + int r; - r = frames = snd_pcm_writei(sound_handle, buffer, N(buffer)); + r = frames = snd_pcm_writei(sound_handle, buffer, N); if (frames < 0) r = frames = snd_pcm_recover(sound_handle, r, 0 /* do not print error reason? */); if (r < 0) { fprintf(stderr, "%s: snd_pcm_writei: %s\n", argv0, snd_strerror(r)); return -1; - } - if ((r > 0) && ((size_t)r < N(buffer))) - printf("%s: short write: expected %zu, wrote %zu\n", argv0, N(buffer), (size_t)frames); + } + if ((r > 0) && ((size_t)r < N)) + printf("%s: short write: expected %zu, wrote %zu\n", argv0, N, (size_t)frames); return 0; } -int send_byte(int c) + +/** + * Transmit a byte. + * + * @param c The byte. + * @return 0 on success, -1 on error. + */ +static int send_byte(int c) { - int low1, high1, low2, high2; - get_freq((c >> 0) & 0x0F, &low1, &high1); - get_freq((c >> 4) & 0x0F, &low2, &high2); - if (send_tones(low1, high1)) - return -1; - if (send_tones(low2, high2)) - return -1; + if (send_nibble((c >> 0) & 0x0F)) return -1; + if (send_nibble((c >> 4) & 0x0F)) return -1; return 0; } -int send_byte_with_ecc(int c) + +/** + * Transmit a byte with error correcting code. + * + * This function uses a buffer so that it can + * create an error correcting code. The bytes + * are not transmitted until this buffer has + * been filled. + * + * @param c The byte, the negative of that byte (intended + * only for `CHAR_END` and `CHAR_CANCEL`) to fill + * the remained of the buffer with the byte. + * Note that if a negative value is used, it is + * no necessary that anything will happen. + * @return 0 on success, -1 on error. + */ +static int send_byte_with_ecc(int c) { - static int cs[4]; + static int data[4]; static int ptr = 0; - int data[8]; - int i; + int code[8]; + int i, rc = 1; + /* Fill buffer. */ if (c < 0) - while (ptr < 4) - cs[ptr++] = -c; + { + if (ptr > 0) + while (ptr < 4) + data[ptr++] = -c; + } else - cs[ptr++] = c; + data[ptr++] = c; + /* Is it full? */ if (ptr < 4) return 0; - ptr = 0; - data[0] = cs[0] ^ cs[1] ^ cs[3]; - data[1] = cs[0] ^ cs[2] ^ cs[3]; - data[2] = cs[0]; - data[3] = cs[1] ^ cs[2] ^ cs[3]; - data[4] = cs[1]; - data[5] = cs[2]; - data[6] = cs[3]; - data[7] = cs[0] ^ cs[1] ^ cs[2] ^ cs[3]; + /* Hamming code. */ + code[0] = data[0] ^ data[1] ^ data[3]; + code[1] = data[0] ^ data[2] ^ data[3]; + code[2] = data[0]; + code[3] = data[1] ^ data[2] ^ data[3]; + code[4] = data[1]; + code[5] = data[2]; + code[6] = data[3]; + code[7] = data[0] ^ data[1] ^ data[2] ^ data[3]; + /* Transmit. */ for (i = 0; i < 8; i++) - if (send_byte(data[i])) + if (send_byte(code[i])) return -1; return 0; } +/** + * Transmit a file over audio. + * + * @param argc Not used for anything else than the process name. + * @param argv Not used for anything else than the process name. + * @return 0 on success, 1 on failure. + */ int main(int argc, char* argv[]) { - int r; + struct sigaction act; char buf[1024]; - int c; + int r, c, rc = 1; ssize_t n, i; - (void) argc; - argv0 = argv[0]; + argv0 = argc ? argv[0] : ""; + /* Set up signal handling. */ + siginterrupt(SIGTERM, 1); + siginterrupt(SIGQUIT, 1); + siginterrupt(SIGINT, 1); + siginterrupt(SIGHUP, 1); + sigemptyset(&(act.sa_mask)); + act.sa_handler = signoop; + act.sa_flags = 0; + sigaction(SIGTERM, &act, NULL); + sigaction(SIGQUIT, &act, NULL); + sigaction(SIGHUP, &act, NULL); + sigprocmask(SIG_SETMASK, &(act.sa_mask), NULL); + + /* Generate the tones to play. */ + init_buffers(); + + /* Set up audio. */ r = snd_pcm_open(&sound_handle, "default", SND_PCM_STREAM_PLAYBACK, 0); if (r < 0) - return - fprintf(stderr, "%s: snd_pcm_open: %s\n", *argv, snd_strerror(r)), - 1; - - r = snd_pcm_set_params(sound_handle, - FORMAT, - SND_PCM_ACCESS_RW_INTERLEAVED, - 1, /* channels */ - SAMPLE_RATE, - 1, /* allow resampling? */ - LATENCY); + return fprintf(stderr, "%s: snd_pcm_open: %s\n", *argv, snd_strerror(r)), 1; + /* Configure audio. */ + r = snd_pcm_set_params(sound_handle, FORMAT, SND_PCM_ACCESS_RW_INTERLEAVED, 1 /* channels */, + SAMPLE_RATE, 1 /* allow resampling? */, LATENCY); if (r < 0) - { - fprintf(stderr, "%s: snd_pcm_set_params: %s\n", *argv, snd_strerror(r)); - goto snd_fail; - } + return fprintf(stderr, "%s: snd_pcm_set_params: %s\n", *argv, snd_strerror(r)), 1; + /* TODO: if reading from the terminal, wait until all input is fetched. */ + /* Send message. */ for (;;) { n = read(STDIN_FILENO, buf, sizeof(buf)); - if (n < 0) - goto fail; - if (n == 0) - break; + if (n < 0) goto fail; + if (n == 0) break; for (i = 0; i < n; i++) { c = buf[i]; if ((c == CHAR_ESCAPE) || (c == CHAR_CANCEL) || (c == CHAR_END)) if (send_byte_with_ecc(CHAR_ESCAPE)) - goto snd_fail; + goto cleanup; if (send_byte_with_ecc(c)) - goto snd_fail; + goto cleanup; } } - if (send_byte_with_ecc(CHAR_END)) - goto snd_fail; - if (send_byte_with_ecc(-CHAR_END)) - goto snd_fail; + /* Mark end of transmission. */ + if (send_byte_with_ecc(CHAR_END)) goto cleanup; + if (send_byte_with_ecc(-CHAR_END)) goto cleanup; - snd_pcm_close(sound_handle); - return 0; + /* Done! */ + rc = 0; + goto cleanup; fail: perror(argv0); - send_byte_with_ecc(CHAR_CANCEL); - send_byte_with_ecc(-CHAR_CANCEL); - return 1; - snd_fail: + cleanup: snd_pcm_close(sound_handle); + /* Mark aborted transmission. */ send_byte_with_ecc(CHAR_CANCEL); send_byte_with_ecc(-CHAR_CANCEL); - return 1; + return rc; } |