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vnlog-parser.c
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vnlog-parser.c
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#define _GNU_SOURCE // for tdestroy()
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <errno.h>
#include <string.h>
#include <stddef.h>
#include <search.h>
#include "vnlog-parser.h"
#define MSG(fmt, ...) \
fprintf(stderr, "%s:%d " fmt "\n", __FILE__, __LINE__, ##__VA_ARGS__)
typedef struct
{
// internal
char* line;
size_t n;
void* dict_key_index;
} vnlog_parser_internal_t;
_Static_assert( sizeof(vnlog_parser_internal_t) <=
sizeof(vnlog_parser_t) - offsetof(vnlog_parser_t, _internal),
"vnlog_parser_internal_t must fit in the allotted space");
static
bool accumulate_legend(// out
int* Ncolumns_allocated,
int* i_col,
vnlog_keyvalue_t** record,
// in
char* str)
{
if(*str == '\0')
// Empty string. Nothing to do
return true;
if(*Ncolumns_allocated <= *i_col)
{
(*Ncolumns_allocated) += 1;
(*Ncolumns_allocated) *= 2;
*record = (vnlog_keyvalue_t*)realloc(*record,
(*Ncolumns_allocated) * sizeof((*record)[0]));
if(*record == NULL)
{
MSG("Couldn't allocate record");
return false;
}
}
(*record)[*i_col].value = NULL;
(*record)[*i_col].key = strdup(str);
if((*record)[*i_col].key == NULL)
return false;
(*i_col)++;
return true;
}
static
bool accumulate_data_row(// out
vnlog_keyvalue_t* record,
int* i_col,
// in
int Ncolumns,
char* str)
{
if(*str == '\0')
// Empty string. Nothing to do
return true;
if(Ncolumns == 0)
{
MSG("Saw data line before a legend line");
return false;
}
if((*i_col) >= Ncolumns)
{
MSG("legend said we have %d columns, but saw a data line that has too many", Ncolumns);
return false;
}
record[(*i_col)++].value = str;
return true;
}
static
vnlog_parser_result_t read_line(vnlog_parser_t* ctx, FILE* fp)
{
int Ncolumns_allocated = 0;
vnlog_parser_internal_t* internal = (vnlog_parser_internal_t*)ctx->_internal;
while(true)
{
if(0 > getline(&internal->line, &internal->n, fp))
{
if(feof(fp))
// done reading file
return VNL_EOF;
MSG("vnl_error reading file: %d", errno);
return VNL_ERROR;
}
// Have one line. Parse it.
char* token;
char* string_to_tokenize = internal->line;
int i_col = 0;
const bool legend_is_done = (ctx->record != NULL);
bool parsing_legend_now = false;
while(NULL != (token = strtok(string_to_tokenize, " \t\n")))
{
string_to_tokenize = NULL;
if(token[0] == '#')
{
if(token[1] == '#' || token[1] == '!')
// hard comment
break;
if(i_col > 0)
// The legend can only appear in the first column
break;
if(legend_is_done)
// Already parsed the legend. The rest of this line is
// comments to be ignored
break;
if(parsing_legend_now)
// We already started the legend. This comment finishes it
break;
// This is the start of the legend. Parse all the columns
parsing_legend_now = true;
if(!accumulate_legend(&Ncolumns_allocated,
&i_col,
&ctx->record,
&token[1]))
return VNL_ERROR;
// grab next token from this line
continue;
}
if(parsing_legend_now)
{
if(!accumulate_legend(&Ncolumns_allocated,
&i_col,
&ctx->record,
token))
return VNL_ERROR;
continue;
}
// Data token
if(!accumulate_data_row(ctx->record,
&i_col,
ctx->Ncolumns,
token))
return VNL_ERROR;
}
// Finished line
if(i_col == 0)
{
// Empty line. Get another.
parsing_legend_now = false;
continue;
}
if(parsing_legend_now)
ctx->Ncolumns = i_col;
else if(i_col != ctx->Ncolumns)
{
MSG("Legend has %d columns, but just saw a data line of %d columns",
ctx->Ncolumns, i_col);
return VNL_ERROR;
}
// Done. All good!
return VNL_OK;
}
MSG("Getting here is a bug");
return VNL_ERROR;
}
static
int compare_record(const vnlog_keyvalue_t* a, const vnlog_keyvalue_t* b)
{
return strcmp(a->key, b->key);
}
static void noop_free(void* _dummy __attribute__((unused)) )
{
}
vnlog_parser_result_t vnlog_parser_init(vnlog_parser_t* ctx, FILE* fp)
{
*ctx = (vnlog_parser_t){};
vnlog_parser_result_t result = read_line(ctx, fp);
if(result != VNL_OK)
{
vnlog_parser_free(ctx);
return result;
}
vnlog_parser_internal_t* internal = (vnlog_parser_internal_t*)ctx->_internal;
// Parsed the legend. Now create a tree to make it easy to look up the
// specific column by key name. Probably these will be called once per run,
// so it could be a simple linear search, but a binary tree is easy-enough
// to use, so I do that
for(int i=0; i<ctx->Ncolumns; i++)
{
if(NULL ==
tsearch( (const void*)&ctx->record[i],
&internal->dict_key_index,
(int(*)(const void*,const void*))compare_record))
return VNL_ERROR;
}
return VNL_OK;
}
void vnlog_parser_free(vnlog_parser_t* ctx)
{
if(ctx != NULL)
{
vnlog_parser_internal_t* internal = (vnlog_parser_internal_t*)ctx->_internal;
free(internal->line);
if(ctx->record != NULL)
{
for(int i=0; i<ctx->Ncolumns; i++)
free(ctx->record[i].key);
}
free(ctx->record);
tdestroy(internal->dict_key_index, &noop_free);
}
*ctx = (vnlog_parser_t){};
}
vnlog_parser_result_t vnlog_parser_read_record(vnlog_parser_t* ctx, FILE* fp)
{
if(ctx == NULL || ctx->record == NULL)
{
MSG("Legend hasn't been read. Call vnlog_parser_init() first");
return VNL_ERROR;
}
vnlog_parser_result_t result = read_line(ctx, fp);
if(result != VNL_OK)
vnlog_parser_free(ctx);
return result;
}
// pointer to the pointer to the string for the record corresponding to the
// given key in the most-recently-parsed row. NULL if the given key isn't found
const char*const* vnlog_parser_record_from_key(vnlog_parser_t* ctx, const char* key)
{
vnlog_parser_internal_t* internal = (vnlog_parser_internal_t*)ctx->_internal;
const vnlog_keyvalue_t*const* keyvalue =
tfind( (const void*)&(const vnlog_keyvalue_t){.key = (char*)key},
&internal->dict_key_index,
(int(*)(const void*,const void*))compare_record);
if(keyvalue == NULL)
return NULL;
return (const char*const*)&(*keyvalue)->value;
}