struct change_header {
	char *message;		/* the "commit" message */
	char *description;	/* the other undescribed part of a change */
	char *timestamp;	/* yes, as a string */
	void *authors;		/* something... */
};

 * The parts of a given change that is blake3-hashed.
 *
 * The actual hashing happens on the serialized (w/bincode) version of this
 * struct. Decoding the 'changes' field will take quite a bit of doing, it's a
 * fairly convoluted field.
 */
struct hashed {
	uint64_t version;	/* same as in offsets? here to be hashed! */
	struct change_header header;
	void *dependencies;	/* array of hashes */
	void *extra_known;	/* another array of hashes */
};
/**

#include "blake3.h"

#include "base32.h"

	printf("%s = [%02x", name, buf[0]);

	printf("%s = [%u", name, buf[0]);

		printf(", %02x", buf[i]);

		printf(", %u", buf[i]);

change_decode_hashed(int fd, size_t comp_hashed_len, size_t hashed_len)

change_decode_hashed(int fd, size_t comp_hashed_len, size_t hashed_len, uint8_t *expected_hash)

	struct hashed hashed;
	blake3_hasher b3sum;
	uint8_t output[BLAKE3_OUT_LEN];
	size_t i;

	/* TODO Decode into 'struct hashed' */
	/* Step 1. Compute the hash of the result buf! */
	blake3_hasher_init(&b3sum);
	blake3_hasher_update(&b3sum, buf, hashed_len);
	blake3_hasher_finalize(&b3sum, output, BLAKE3_OUT_LEN);
	for (i = 0; i < BLAKE3_OUT_LEN; i++)
		printf("%02x", output[i]);
	printf("\n");
	if (expected_hash != NULL) {
		for (i = 0; i < BLAKE3_OUT_LEN; i++)
			printf("%02x", expected_hash[i]);
		printf("\n");
	}

	uint8_t contents_hash[32];

	base32_decode_hash(contents_hash, hash);

	err = change_decode_hashed(fd, off.unhashed_off - OFFSETS_SIZE, off.hashed_len);

	err = change_decode_hashed(fd, off.unhashed_off - OFFSETS_SIZE, off.hashed_len, contents_hash);

#ifndef BASE32_H
#define BASE32_H
/**
 * Takes care of decoding a base32-encoded blake3 hash sum.
 *
 * The input is assumed to be an array of 53 base32 characters, dst is assumed
 * to be able to hold at least 32 bytes.
 */
void base32_decode_hash(uint8_t *dst, char const *in);
#endif

#include <stdint.h>
/**
 * Inspired by the base32 implementation here:
 *
 * https://sourceforge.net/p/cyoencode/code/HEAD/tree/trunk/src/CyoDecode.c
 *
 * Basically, the idea is to allocate a much too large array, fill it with 0xff
 * and plug in the values from the alphabet in their corresponding holes.
 */
static uint8_t BASE32[0x80] = {
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 
	0xff, 0xff, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 
	0xff, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 
	0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 
	0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 
	0x17, 0x18, 0x19, 0xff, 0xff, 0xff, 0xff, 0xff, 
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
};
void
base32_decode_hash(uint8_t *dst, char const *in)
{
	int i, r, off;
	uint8_t v[8];
	for (r = 0; r < 6; r++) {
		off = 8 * r;
		for (i = 0; i < 8; i++)
			v[i] = BASE32[(int)in[off + i]];
		off = 5 * r;
		dst[off]   = v[0] << 3 | v[1] >> 2;
		dst[off+1] = v[1] << 6 | v[2] << 1 | v[3] >> 4;
		dst[off+2] = v[3] << 4 | v[4] >> 1;
		dst[off+3] = v[4] << 7 | v[5] << 2 | v[6] >> 3;
		dst[off+4] = v[6] << 5 | v[7];
	}
	/* decode the remaining two bytes */
	off = 48; /* 6×8 */
	for (i = 0; i < 5; i++)
		v[i] = BASE32[(int)in[off+i]];
	off = 30; /* 6×5 */
	dst[off]   = v[0] << 3 | v[1] >> 2;
	dst[off+1] = v[1] << 6 | v[2] << 1 | v[3] >> 4;
}

OBJS += base32.o