dazibao/src/hash.c

#include "hash.h"

// Hash a single data
void hash_data(pub_data *data, unsigned char *buf) {
	// All three fields are concatenated into a single buffer
	int totlen = data->length + 10;
	unsigned char concat[totlen];
	concat_data(data, concat);

	// The resulting buf is hashed and put into a buffer
	unsigned char hash[SHA256_DIGEST_LENGTH];
	SHA256(concat, totlen, hash);

	// Put truncated hash into buf
	hash_trunc(hash, buf);
}

// Hash every data contained in data_list then return a network hash
void hash_network(list *data_list, unsigned char *buf) {
	// Get list length to initialize concat buffer
	int concat_len = len_list(data_list) * 16;
	unsigned char *concat = (unsigned char*) malloc(concat_len);

	unsigned char hash[SHA256_DIGEST_LENGTH];
	int totlen = 0;
	list *tmp = data_list;

	// Hash every known data and concatenate it to buffer concat
	while(tmp != NULL) {
		hash_data((pub_data*) tmp->data, hash);
		concat_hash(concat, hash, totlen);
		totlen += 16;
		tmp = tmp->next;
	}

	// Hash all of concat to obtain the network hash
	SHA256(concat, totlen, hash);

	// Put truncated hash into buf
	hash_trunc(hash, buf);

	// Get rid of concat
	free(concat);
}

// Truncate 32 octet hash to 16 octets
void hash_trunc(unsigned char *hash32oct, unsigned char *buf) {
	// Copy the first 16 octets from hash32oct
	memcpy(buf, hash32oct, 16);
}

// Concat all fields of data and put them in buf
void concat_data(pub_data *data, unsigned char *buf) {
	memcpy(buf, &(data->id), 8);
	memcpy(buf+8, &(data->seqno), 2);
	memcpy(buf+10, data->data, data->length);
}

// Concat hash2 to hash1 (hash1 is modified)
void concat_hash(unsigned char *hash1, unsigned char *hash2, size_t size) {
	memcpy(hash1+size, hash2, 16);
}