Initial commit

add project structure, Makefile and initial code to write wave files

.gitignore

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+build/
+*.o
+src/test.c

LICENSES/GPL-2.0-only.txt

@@ -0,0 +1,319 @@
+GNU GENERAL PUBLIC LICENSE
+
+Version 2, June 1991
+
+Copyright (C) 1989, 1991 Free Software Foundation, Inc. 
+
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
+
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+Preamble
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+The licenses for most software are designed to take away your freedom to share
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+
+<signature of Ty Coon >, 1 April 1989 Ty Coon, President of Vice This General
+Public License does not permit incorporating your program into proprietary
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+useful to permit linking proprietary applications with the library. If this
+is what you want to do, use the GNU Lesser General Public License instead
+of this License.

Makefile

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+CC ?= gcc
+CFLAGS ::= $(CFLAGS) -std=c99 -Wall -pedantic
+DEPS = src/wavfile.h
+
+build/%.o: src/%.c $(DEPS)
+	$(CC) -c -o $@ $< $(CFLAGS)
+all: build/wavfile.o build/test.o
+	$(CC) -o build/test build/wavfile.o build/test.o
+
+.PHONY: clean
+clean:
+	rm -f build/*.o
+	rm -f build/test

src/wavfile.c

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+/*
+ * SPDX-FileCopyrightText: 2019 Helmut Pozimski <helmut@pozimski.eu>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ */
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdint.h>
+
+#include "wavfile.h"
+
+
+/* Important constants that represent chunk IDs or other
+ * parts of the wave file
+ */
+#define RIFF 0x46464952
+#define WAVE 0x45564157
+#define FMT 0x20746d66
+#define DATA 0x61746164
+#define MAX_DATA_BYTES 4294967295
+
+/* struct definitions for the chunk types in a wave file */
+
+/* common header for all chunks */
+typedef struct {
+	uint32_t chunk_id;
+	uint32_t chunk_size;
+} chunk_header;
+
+/* riff chunk at the beginning of the file */
+typedef struct {
+	chunk_header riff_header;
+        uint32_t riff_format;
+} riff_chunk;
+
+/* format sub-chunk */
+typedef struct {
+	chunk_header format_header;
+        uint16_t audioformat;
+        uint16_t num_channels;
+        uint32_t sample_rate;
+        uint32_t byte_rate;
+        uint16_t block_align;
+        uint16_t bits_per_sample;
+} format_chunk;
+
+#define io_error_check(x, y) { if (x == -1) { free(y); return NULL; } }
+/*
+ * Function: wavfile_create
+ * --------------------------
+ *     Creates a wave file and writes the basic chunks into it
+ *
+ * file_name: name and path of the file to create
+ * channels: number of sound channels
+ * sample_rate: sampling rate for the audio data
+ * bits_per_sample: bit width of one sample
+ *
+ * returns: a structure representing a wave file
+ */
+wavfile * wavfile_create(const char * file_name, uint16_t channels, uint32_t sample_rate, uint32_t bits_per_sample) {
+	wavfile * file = malloc(sizeof(wavfile));
+	if (file == NULL) {
+		return NULL;
+	}
+	int fd = open(file_name, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+	if (fd == -1 ) {
+		return NULL;
+	}
+	file->fd = fd;
+	file->data_bytes_written = 0;
+	riff_chunk riff_chunk = {
+		.riff_header = {
+			.chunk_id = RIFF,
+			.chunk_size = 0
+		},
+		.riff_format = WAVE
+	};
+	io_error_check(write(fd, &riff_chunk, sizeof(riff_chunk)), file);
+	format_chunk format_chunk =  {
+		.format_header = {
+			.chunk_id = FMT,
+			.chunk_size = 16
+		},
+		.audioformat = 1,
+		.num_channels = channels,
+		.sample_rate = sample_rate,
+		.byte_rate = sample_rate * channels * (bits_per_sample / 8),
+		.block_align = channels * (bits_per_sample / 8),
+		.bits_per_sample = bits_per_sample
+	};
+	io_error_check(write(fd, &format_chunk, sizeof(format_chunk)), file);
+	chunk_header data_header = {
+		.chunk_id = DATA,
+		.chunk_size = 0
+	};
+	io_error_check(write(fd, &data_header, sizeof(chunk_header)), file);
+	return file;	
+}
+
+/*
+ * Function: wavfile_append_data
+ * --------------------------
+ *     Appends an arbitrary amount of data to the data
+ *     section of a wave file
+ *
+ * file: pointer to the file structure
+ * data: pointer to the data to be written
+ * num_bytes: number of bytes to be written
+ *
+ * returns: an integer representing the number of bytes written
+ */
+int wavfile_append_data(wavfile * file, void * data, uint32_t num_bytes) {
+	uint32_t written;
+	if (num_bytes + file->data_bytes_written > MAX_DATA_BYTES) {
+		return 0;
+	}
+	written = write(file->fd, data, num_bytes);
+	file->data_bytes_written += written;
+	return written;
+}
+
+/*
+ * Function: wavfile_close
+ * -----------------------
+ *    Closes the file descriptor of a wave file
+ *    and writes the size information in the relevant chunks
+ *
+ * file: pointer to the file structure
+ *
+ * returns: 0 on success and -1 on failure
+ */
+int wavfile_close(wavfile * file) {
+	int err = 0;
+	lseek(file->fd, 4, SEEK_SET);
+	uint32_t file_size = 36 + file->data_bytes_written;
+	err = write(file->fd, &file_size, 4);
+	if (err == -1) {
+		return err;
+	}
+	lseek(file-> fd, 40, SEEK_SET);
+	err = write(file->fd, &file->data_bytes_written, 4);
+	if (err == -1) {
+		return err;
+	}
+	err = close(file->fd);
+	free(file);
+	return err;
+}

src/wavfile.h

@@ -0,0 +1,18 @@
+/*
+ * SPDX-FileCopyrightText: 2019 Helmut Pozimski <helmut@pozimski.eu>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ */
+
+#include <stdint.h>
+
+/* struct that represents a wave file */
+typedef struct {
+	int fd;
+	uint32_t data_bytes_written;
+} wavfile;
+
+/* function prototypes */
+wavfile * wavfile_create(const char * file_name, uint16_t channels, uint32_t sample_rate, uint32_t bits_per_sample);
+int wavfile_append_data(wavfile * file, void * data, uint32_t num_bytes);
+int wavfile_close(wavfile * file);