ffdb/trie.c

#include "trie.h"

#include "json/json.h"

#include <stdlib.h>
#include <string.h>

struct edge {
	char* label;
	char* value;
	int count;
};

/*
{
	"k": "test",
	"t": 2,
	"z": 7
}

*/

struct trie_entry
{
	struct {
		struct edge* items;
		int count;
	} edges;
	char* filename;
};

static void trie_entry_free( struct trie_entry* e )
{
	if( !e ) { return; }

	for( int i = 0; i < e->edges.count; ++i ) {
		free(e->edges.items[i].label);
		free(e->edges.items[i].value);
	}
	free(e->edges.items);
	free(e->filename);
	free(e);
}

static bool trie_entry_load( FILE* f, struct trie_entry* e )
{
	struct json_pull_parser jpp = {
		.f = f,
		.curr_state = jpp_initial_state,
	};
	if( !jpp.f ) { return false; }

	int save;
	if( !json_pull_parser_begin_object(&jpp,&save) ) { goto failed; }

	e->edges.count = 0;

	char* edge_label = NULL;
	while( edge_label = json_pull_parser_read_object_key(&jpp) ) {
		e->edges.count += 1;
		e->edges.items = realloc( e->edges.items, sizeof(struct edge) * e->edges.count );
		struct edge* ed = &e->edges.items[ e->edges.count-1 ];
		memset(ed,0,sizeof(*ed));

		ed->label = edge_label;
		ed->count = 1;
		if( !json_pull_parser_read_int( &jpp, &ed->count ) ) {
			char* value = json_pull_parser_read_string(&jpp);
			if( !value ) { goto failed; }

			ed->value = value;
		}
	}

	if( !json_pull_parser_end_object(&jpp,&save) ) { goto failed; }

	return true;
failed:
	fclose(jpp.f);
	return false;
}
static bool trie_entry_load_from_file( const char* filename, struct trie_entry* e )
{
	e->filename = strdup(filename);

	FILE* f = fopen( filename, "r" );
	if( !f ) { return false; }

	bool result = trie_entry_load( f, e );
	fclose(f);

	return result;
}

static void trie_entry_save( FILE* f, struct trie_entry* e )
{
	fprintf( f, "{" );
	for( int i = 0; i < e->edges.count; ++i ) {
		if( i != 0 ) {
			fprintf( f, ",\n\t" );
		} else {
			fprintf( f, "\n\t" );
		}

		struct edge* ed = &e->edges.items[i];
		json_write_string( f, ed->label );
		fprintf( f, ": " );
		if( ed->count > 1 ) {
			fprintf( f, "%d", ed->count );
		} else {
			json_write_string( f, ed->value );
		}
	}
	fprintf( f, "\n}\n" );
}
static bool trie_entry_save_to_file( const char* filename, struct trie_entry* e )
{
	char tmp_filename[512];
	snprintf( tmp_filename, sizeof(tmp_filename), "%s.tmp", filename );
	FILE* f = fopen(tmp_filename,"w");
	if( !f ) { return false; }

	trie_entry_save( f, e );

	fclose(f);
	rename( tmp_filename, filename );
	return true;
}

// Escape '/' as "%|" and '%' as "%%"
static char* escape( const char* str )
{
	int size = 0;
	for( const char* i = str; *i; ++i ) {
		switch( *i ) {
			case '/': size += 2; break;
			case '%': size += 2; break;
			default:  size += 1; break;
		}
	}

	char* result = malloc(size+1);
	char* o = result;
	for( const char* i = str; *i; ++i ) {
		switch( *i ) {
			case '/':
				o[0] = '%';
				o[1] = '|';
				o += 2;
				break;
			case '%':
				o[0] = '%';
				o[1] = '%';
				o += 2;
				break;
			default:
				*o = *i;
				++o;
		}
	}
	*o = '\0';

	return result;
}

static int prefix_match( const char* a, const char* b )
{
	int res = 0;
	while( *a && *b && *a == *b ) {
		a += 1;
		b += 1;
		res += 1;
	}
	return res;
}

static bool trie_entry_set( struct trie_entry* e, const char* key, const char* value )
{
	int prefix_len = 0;
	struct edge* ed;

	printf( "key: %s\n", key );
	for( int i = 0; i < e->edges.count; ++i ) {
		ed = &e->edges.items[i];
		printf( "label[%d]: %s\n", i, ed->label );
		fflush(stdout);

		prefix_len = prefix_match( key, ed->label );
		if( prefix_len == strlen( ed->label ) ) {
			goto traverse_existing_edge;
		} else if( prefix_len != 0 ) {
			goto split_existing_edge;
		}
	}

	goto add_new_edge;

add_new_edge:
	{
		printf( "Adding edge %s\n", key );
		e->edges.count += 1;
		e->edges.items = realloc( e->edges.items, sizeof(struct edge) * e->edges.count );

		struct edge* ed2 = &e->edges.items[e->edges.count-1];
		ed2->label = strdup(key);
		ed2->value = strdup(value);
		ed2->count = 1;
	}
	return trie_entry_save_to_file( e->filename, e );

traverse_existing_edge:
	if( ed->count == 1 ) {
		free(ed->value);
		ed->value = strdup(value);
		return true;
	}

	printf( "TODO: exact match, go down this node\n" );
	return false;

split_existing_edge:
	{
		char* new_prefix = strndup( key, prefix_len );
		char* new_filename = malloc(strlen(e->filename)+prefix_len+1);
		strcpy(new_filename,e->filename);
		strcat(new_filename,new_prefix);

		// Create the new node
		struct trie_entry* new_e = malloc(sizeof(struct trie_entry));
		memset(new_e,0,sizeof(*new_e));
		new_e->filename = new_filename;

		new_e->edges.items = malloc( sizeof(struct edge) * 2 );
		new_e->edges.items[0].label = strdup(&ed->label[prefix_len]);
		new_e->edges.items[0].value = ed->value;
		new_e->edges.items[0].count = 1;

		new_e->edges.items[1].label = strdup(&key[prefix_len]);
		new_e->edges.items[1].value = strdup(value);
		new_e->edges.items[1].count = 1;
		new_e->edges.count = 2;

		// Save to file
		trie_entry_save_to_file( new_e->filename, new_e );
		trie_entry_free(new_e);

		// Update the existing edge
		free(ed->label);
		ed->label = new_prefix;
		ed->value = NULL;
		ed->count = 2;
		trie_entry_save_to_file( e->filename, e );
	}
	return true;
}

static struct trie_entry* load_root_node( const char* filename )
{
	struct trie_entry* root = malloc(sizeof(*root));
	memset(root,0,sizeof(*root));

	char buffer[512];
	snprintf( buffer, sizeof(buffer), "%s/%ROOT|", filename );
	trie_entry_load_from_file( buffer, root );

	return root;
}

bool ffdb_trie_set( const char* filename, const char* key, const char* value )
{
	struct trie_entry* root = NULL;
	char* key_escaped = escape(key);
	bool result = false;

	root = load_root_node(filename);

	if( !trie_entry_set( root, key_escaped, value ) ) {
		printf( "Failed to set %s to %s\n", key, value );
		goto failed;
	}

	result = true;
cleanup:
	free(key_escaped);
	trie_entry_free(root);
	return result;
failed:
	result = false;
	goto cleanup;
}
char* ffdb_trie_get( const char* filename, const char* key )
{
	return NULL;
}
bool ffdb_trie_remove( const char* filename, const char* key )
{
	return false;
}
int ffdb_trie_count( const char* filename )
{
	struct trie_entry* root = NULL;
	int result = 0;

	root = load_root_node(filename);
	if( !root ) { goto failed; }

	for( int i = 0; i < root->edges.count; ++i ) {
		result += root->edges.items[i].count;
	}
cleanup:
	trie_entry_free(root);
	return result;
failed:
	result = -1;
	goto cleanup;
}

void ffdb_trie_clean( const char* filename )
{
}