[towel-db commit] r28 - trunk/c
codesite...@google.com
Date: Fri Jun 13 11:58:44 2008
New Revision: 28
Modified:
trunk/c/parser.c
trunk/c/toweldb.h
Log:
Redesign record parsing code from scratch. Very much still a WIP.
Modified: trunk/c/parser.c
==============================================================================
--- trunk/c/parser.c (original)
+++ trunk/c/parser.c Fri Jun 13 11:58:44 2008
@@ -17,51 +17,28 @@
#include "toweldb.h"
-const char* TOWELDB_HEADER_TOKEN = "\n%%";
+#define TOWELDB_COMPONENT_NONE 0
+#define TOWELDB_COMPONENT_KEY 1
+#define TOWELDB_COMPONENT_DATA 2
-void toweldb_push_stack( char* stack, unsigned short stack_len, char
new_char )
-{
- unsigned short i = 0;
- unsigned short stack_max = (stack_len - 2);
-
- /* Push back the current stack */
- for( i = 0; i < stack_max; i++ )
- {
- stack[i] = stack[i+1];
- }
-
- /* Add the new char */
- stack[stack_max] = new_char;
- stack[stack_max+1] = '\0';
-}
+#define TOWELDB_PHASE_NULL 0
+#define TOWELDB_PHASE_START 1
+#define TOWELDB_PHASE_HALFWAY 2
+#define TOWELDB_PHASE_FINISH 3
toweldb_rec*
toweldb_read_rec( toweldb_db* db, const char* key )
-{
+{
char* path = NULL;
toweldb_rec* rec = NULL;
- FILE* rec_f = NULL;
- const short stack_len = 4;
-
- /* Array allocation information */
- unsigned int n_fields = 0;
- unsigned int header_len = 0;
- unsigned long field_len = 0;
-
- /* Parsing data */
+ FILE* rec_file = NULL;
+ struct stat rec_info;
+ off_t rec_len = 0;
+ off_t current_char = 0;
+ char* rec_contents = NULL;
toweldb_field_node* cur_node = NULL;
- bool header = true;
- bool in_field = false;
- unsigned int i = 0;
- char current_char = 0;
-
- /* A small cache stack to store recently read characters */
- char* read_cache = malloc( sizeof( char ) * stack_len );
- for( i = 0; i < (stack_len-1); i++ )
- {
- read_cache[i] = 0;
- }
- read_cache[stack_len-1] = '\0';
+ char token_phase = 0;
+ char rec_component = TOWELDB_COMPONENT_NONE;
/* Allocate the data structure */
rec = malloc( sizeof( toweldb_rec ));
@@ -71,96 +48,106 @@
rec->contents_start = malloc( sizeof( toweldb_field_node ));
cur_node = rec->contents_start;
+ cur_node->key_len = 0;
+ cur_node->value_len = 0;
cur_node->key = NULL;
cur_node->value = NULL;
cur_node->next = NULL;
/* Open the record */
path = toweldb_get_path( db, key );
- if(( rec_f = fopen( path, "r" )) == NULL )
+ if(( rec_file = fopen( path, "r" )) == NULL )
{
/* Something's wrong. Let's skip town, shall we? */
return NULL;
}
- /* Parse the record. I admit it: this is the most bizarre code that
has no
- * business actually working. Basically, the main loop only exists to
- * stop the parsing at the end of the file and to start the various
- * sub-loops. */
- /* TODO: Allow escaping */
-
- /* Prepare for the loop */
- /* Push back the current character stack */
- toweldb_push_stack( read_cache, stack_len, fgetc( rec_f ));
+ /* Figure out how large the file is so we can load it into memory */
+ if( stat( path, &rec_info ))
+ {
+ return NULL;
+ }
+ else
+ {
+ rec_len = rec_info.st_size;
+ }
- while( read_cache[2] != EOF )
- {
- /* Figure out if we've got a header on our hands */
- if( !strcmp( read_cache, TOWELDB_HEADER_TOKEN ))
+ /* Copy the file into memory */
+ rec_contents = malloc( sizeof( char ) * rec_len );
+ for( current_char = 0; current_char < rec_len; current_char++ )
+ {
+ rec_contents[current_char] = fgetc( rec_file );
+
+ /* Parsing works kind of crazily currently. A header token has three
+ * characters: \n%%. token_phase holds the number of characters that
+ * have been matched so far. So here we look at that */
+ if( rec_contents[current_char] == '\n' )
{
- header = true;
- in_field = true;
+ /* If we're already in a key, then this should end it */
+ if( rec_component == TOWELDB_COMPONENT_KEY )
+ {
+ rec_component = TOWELDB_COMPONENT_DATA;
+ }
+
+ if( !token_phase )
+ token_phase = TOWELDB_PHASE_START;
+ }
+ else if( rec_contents[current_char] == '%' )
+ {
+ if( token_phase < TOWELDB_PHASE_FINISH )
+ token_phase++;
}
else
{
- header = false;
+ if( token_phase )
+ token_phase = TOWELDB_PHASE_NULL;
}
- if( header )
+ /* If we've got a complete token, then mark our location */
+ if( token_phase == TOWELDB_PHASE_FINISH )
{
- /* Initialize the current_char variable for this iteration */
- current_char = read_cache[2];
-
- /* Figure out how long the header is */
- while( current_char != '\n' )
- {
- current_char = fgetc( rec_f );
- header_len++;
- };
-
- /* Go back to the start of the header */
- fseek( rec_f, (-header_len), SEEK_CUR );
-
- /* Allocate the header string */
- cur_node->key = malloc( sizeof( char ) * ( header_len + 1 ));
-
- /* Copy the header string into the allocated memory block. However,
- * header_len needs to be one less since our array counts from 0 */
- header_len--;
- for( i = 0; i < header_len; i++ )
+ /* If we haven't hit a key yet, then we don't want to allocate a
+ * new data structure */
+ if( rec_component != TOWELDB_COMPONENT_NONE )
{
- cur_node->key[i] = fgetc( rec_f );
+ /* Our length calculations for the previous data includes the
+ * header token. Let's ditch that... */
+ cur_node->value_len -= TOWELDB_PHASE_FINISH;
+
+ /* We need a new field node */
+ cur_node->next = malloc( sizeof( toweldb_field_node ));
+ cur_node = cur_node->next;
+ cur_node->key_len = 0;
+ cur_node->value_len = 0;
+ cur_node->key = NULL;
+ cur_node->value = NULL;
+ cur_node->next = NULL;
}
- cur_node->key[i] = '\0';
-
- /* Skip to the next line */
- fseek( rec_f, 1, SEEK_CUR );
- /* Allocate the next field node */
- cur_node->next = malloc( sizeof( toweldb_field_node ));
- cur_node->next->key = NULL;
- cur_node->next->value = NULL;
- cur_node->next->next = NULL;
- cur_node = cur_node->next;
+ /* Mark the location of the end of the token */
+ cur_node->key_loc = current_char;
- /* Reset our variables */
- header_len = 0;
+ /* It's official: we are in a key */
+ rec_component = TOWELDB_COMPONENT_KEY;
}
- else if( in_field )
+
+ /* Increment the length variables as needed */
+ if( rec_component == TOWELDB_COMPONENT_KEY )
{
- /* We need to read the contents of the field. First let's figure
- * out how long it is */
- printf( "%c", read_cache[2] );
+ cur_node->key_len++;
+ printf( "%c\n", rec_contents[current_char] );
+ }
+ else if( rec_component == TOWELDB_COMPONENT_DATA )
+ {
+ /* We aren't in a key, so we need to increment the data length */
+ cur_node->value_len++;
}
-
- /* Go to the next character in the file */
- toweldb_push_stack( read_cache, stack_len, fgetc( rec_f ));
}
-
+
/* Wrap up */
- fclose( rec_f );
+ fclose( rec_file );
free( path );
- free( read_cache );
+ free( rec_contents );
return rec;
}
Modified: trunk/c/toweldb.h
==============================================================================
--- trunk/c/toweldb.h (original)
+++ trunk/c/toweldb.h Fri Jun 13 11:58:44 2008
@@ -52,6 +52,9 @@
/* Linked list of record fields */
typedef struct _toweldb_tuple
{
+ off_t key_loc;
+ unsigned int key_len;
+ unsigned long value_len;
char* key;
char* value;
struct _toweldb_tuple* next;