shithub: rgbds

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Record "seed" when generating images as well

For reproducibility

--- a/test/randtilegen.c

+++ b/test/randtilegen.c

@@ -22,13 +22,14 @@

 #include <stdlib.h>

 #include <string.h>

+FILE *rngRecorder; // File to which the random bytes will be read

 uint32_t randBits = 0; // Storage for bits read from the input stream but not yet used

 uint8_t randCount = 0; // How many bits are currently stored in the above

-size_t nbRandBytes = 0;

 static uint32_t getRandomBits(uint8_t count) {

-	// Trying to read one more byte with `randCount` at least this high will drop some bits

-	// If the count is no higher than that limit, then the loop will exit without reading more bytes

+	// Trying to read one more byte with `randCount` at least this high will drop some bits!

+	// If the count is no higher than that limit, then the loop is guaranteed to exit without

+	// reading more bytes.

 	assert(count <= sizeof(randBits) * 8 + 1);

 	// Read bytes until we have enough bits to serve the request

@@ -35,12 +36,11 @@

 	while (count > randCount) {

 		int data = getchar();

 		if (data == EOF) {

-			fprintf(stderr, "Exit after reading %zu bytes\n", nbRandBytes);

 			exit(0);

 		}

 		randBits |= (uint32_t)data << randCount;

 		randCount += 8;

-		++nbRandBytes;

+		fputc(data, rngRecorder);

 	}

 	uint32_t result = randBits & (((uint32_t)1 << count) - 1);

@@ -50,6 +50,14 @@

 }

 /**

+ * Flush any remaining bits in the RNG storage

+ */

+static void flushRng(void) {

+	randCount = 0;

+	randBits = 0;

+}

+

+/**

  * Expand a 5-bit color component to 8 bits with minimal bias

  */

 static uint8_t _5to8(uint8_t five) {

@@ -203,10 +211,17 @@

 		}

 	}

-	char filename[maxBasenameLen + 25];

+	char filename[maxBasenameLen + sizeof("65535.png")];

 	for (uint16_t i = 0;; i++) { // 65k images ought to be enough

 		for (int index = 1; index < argc; index++) {

-			sprintf(filename, "%s%" PRIu16 ".png", argv[index], i);

+			int len = sprintf(filename, "%s%" PRIu16 ".rng", argv[index], i);

+			rngRecorder = fopen(filename, "wb");

+			if (!rngRecorder) {

+				perror("RNG fopen");

+				return 1;

+			}

+

+			filename[len - 3] = 'p'; // `.rng` -> `.png`

 			FILE *img = fopen(filename, "wb");

 			if (!img) {

 				perror("PNG fopen");

@@ -227,10 +242,15 @@

 				return 1;

 			}

+			// Ensure that image generation starts on byte boundaries

+			// (This is necessary so that all involved random bits are recorded in the `.rng` file)

+			flushRng();

+

 			png_init_io(png, img);

 			generate_random_image(png, pngInfo);

 			png_destroy_write_struct(&png, &pngInfo);

 			fclose(img);

+			fclose(rngRecorder);

 		}

 		if (i == UINT16_MAX) {