template.c: refactor code and change initial type of w

documentation.md

@@ -3,5 +3,5 @@
 ## Bytebeat code
 
 **Variables:**
-- `w`: `long double`
+- `w`: a `size_t` variable casted as `long double`
 - `t`: `w` casted as `uintmax_t`

src/template.c

@@ -127,30 +127,37 @@ main(int argc, char** argv)
 	}
 
 	// * allocate heap for sample data
-	SAMPLE_TYPE* q = calloc(PRODUCT, sizeof(SAMPLE_TYPE));
+	SAMPLE_TYPE* buffer = calloc(PRODUCT, sizeof(SAMPLE_TYPE));
 
-	if (q == NULL)
+	if (buffer == NULL) {
+		perror("calloc");
 		return 1;
+	}
 
 	debug_print();
 
 	// * bytebeat generating loop
-	for (uintmax_t w = 0; w < PRODUCT; w++) {
+	for (size_t w = 0; w < PRODUCT; w++) {
 		// 1. generate audio data
-		long double res = bytebeat((long double)w);
+		long double bytebeat_res = bytebeat((long double)w);
 
 		// 2. if signed, then wrap up into unsigned
 		if (IS_SIGNED)
-			q[w] = (SAMPLE_TYPE)signed_to_unsigned(res) & BIT_DEPTH_LIMITER;
-		else
-			q[w] = (SAMPLE_TYPE)res & BIT_DEPTH_LIMITER;
+			bytebeat_res = signed_to_unsigned(bytebeat_res);
+
+		// 3. convert audio data to sample
+		SAMPLE_TYPE sample_res = (SAMPLE_TYPE)bytebeat_res &
+			BIT_DEPTH_LIMITER;
 
 		// 4. if bit depth is less than 8, stretch it
 #if BIT_DEPTH < 8
-		q[(size_t)w] = (SAMPLE_TYPE)((long double)q[(size_t)w] *
-									 ((long double)BIT_DEPTH / 8.0));
+		sample_res = (SAMPLE_TYPE)
+			((long double)buffer[w] * ((long double)BIT_DEPTH / 8.L));
 #endif
 
+		// 5. save sample into buffer
+		buffer[w] = sample_res;
+
 		// 6. log
 		if (
 		  !silent_mode &&
@@ -174,36 +181,50 @@ main(int argc, char** argv)
 	fflush(stdout);
 
 	// 1. open file
-	FILE* r = fopen("output.wav", "wb");
+	FILE* output_file = fopen("output.wav", "wb");
 
-	if (r == NULL || !r)
+	if (output_file == NULL || !output_file) {
+		perror("fopen");
 		return 1;
+	}
 
-	// 2. write headers and data
-	fwrite("RIFF", 1, 4, r);
-	uint32_t t = PRODUCT;
-	fwrite(&t, sizeof(t), 1, r);
-	fwrite("WAVE", 1, 4, r);
-	fwrite("fmt ", 1, 4, r);
-	uint32_t y = 16; // what? 16-bit depth? or [something else]?
-	fwrite(&y, sizeof(y), 1, r);
-	uint16_t u = 1; // 1 what? 1 = unsigned?
-	fwrite(&u, sizeof(u), 1, r);
-	uint16_t i = CHANNELS;
-	fwrite(&i, sizeof(i), 1, r);
-	uint32_t o = SAMPLE_RATE;
-	fwrite(&o, sizeof(o), 1, r);
-	uint32_t s = SAMPLE_RATE * i;
-	fwrite(&s, sizeof(s), 1, r);
-	uint16_t p = i;
-	fwrite(&p, sizeof(p), 1, r);
-	uint16_t a = BIT_DEPTH >= 8 ? BIT_DEPTH : 8;
+	// 2. prepare variables
+	const uint32_t buffer_size = PRODUCT,
+		file_length =
+			4 * 4   /* 4 strings of 4 characters */ +
+			4 * 4   /* 4 uint32_t values */         +
+			5 * 2   /* 5 uint16_t values */         +
+			PRODUCT /* sample data */,
+		fmt_data_length = 16 /* length of format data before this value
+								in the file format structure */,
+		sample_rate = SAMPLE_RATE;
+	const uint16_t fmt_type = 1, // format type is PCM
+		channels = CHANNELS,
+		byte_rate = (SAMPLE_RATE * BIT_DEPTH * CHANNELS) / 8,
+		block_align = (BIT_DEPTH * CHANNELS) / 8,
+		bit_depth = BIT_DEPTH > 8 ? BIT_DEPTH : 8;
 
-	fwrite(&a, sizeof(a), 1, r);
-	fwrite("data", 1, 4, r);
-	fwrite(&t, sizeof(t), 1, r);
-	fwrite(q, sizeof(uint8_t), PRODUCT, r);
-	fclose(r);
+	// 3. write headers
+	// <L = Little-endian or B = Big-endian> : <name> : <bytes of field>
+	fwrite("RIFF",           1, 4, output_file); // B : ChunkID       : 4
+	fwrite(&file_length,     4, 1, output_file); // L : ChunkSize     : 4
+	fwrite("WAVE",           1, 4, output_file); // B : Format        : 4
+	fwrite("fmt ",           1, 4, output_file); // B : Subchunk1ID   : 4
+	fwrite(&fmt_data_length, 4, 1, output_file); // L : Subchunk1Size : 4
+	fwrite(&fmt_type,        2, 1, output_file); // L : AudioFormat   : 2
+	fwrite(&channels,        2, 1, output_file); // L : NumChannels   : 2
+	fwrite(&sample_rate,     4, 1, output_file); // L : SampleRate    : 4
+	fwrite(&byte_rate,       4, 1, output_file); // L : ByteRate      : 4
+	fwrite(&block_align,     2, 1, output_file); // L : BlockAlign    : 2
+	fwrite(&bit_depth,       2, 1, output_file); // L : BitsPerSample : 2
+	fwrite("data",           1, 4, output_file); // B : Subchunk2ID   : 4
+	fwrite(&buffer_size,     4, 1, output_file); // B : Subchunk2Size : 4
+
+	// 4. write sample data
+	fwrite(buffer, sizeof(SAMPLE_TYPE), buffer_size, output_file);
+
+	// 5. close file
+	fclose(output_file);
 	debug_print();
 
 	// * end of program