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/* src/interfaces/ecpg/ecpglib/prepare.c */

#define POSTGRES_ECPG_INTERNAL
#include "postgres_fe.h"

#include <ctype.h>

#include "ecpgtype.h"
#include "ecpglib.h"
#include "ecpgerrno.h"
#include "extern.h"
#include "sqlca.h"

#define STMTID_SIZE 32

typedef struct
{
int lineno;
char stmtID[STMTID_SIZE];
char *ecpgQuery;
long execs; /* # of executions */
const char *connection; /* connection for the statement */
} stmtCacheEntry;

static int nextStmtID = 1;
static const int stmtCacheNBuckets = 2039; /* # buckets - a prime # */
static const int stmtCacheEntPerBucket = 8; /* # entries/bucket */
static stmtCacheEntry stmtCacheEntries[16384] = {{0, {0}, 0, 0, 0}};

static bool deallocate_one(int lineno, enum COMPAT_MODE c, struct connection * con,
struct prepared_statement * prev, struct prepared_statement * this);

static bool
isvarchar(unsigned char c)
{
if (isalnum(c))
return true;

if (c == '_' || c == '>' || c == '-' || c == '.')
return true;

if (c >= 128)
return true;

return (false);
}

static bool
replace_variables(char **text, int lineno)
{
bool string = false;
int counter = 1,
ptr = 0;

for (; (*text)[ptr] != '\0'; ptr++)
{
if ((*text)[ptr] == '\'')
string = string ? false : true;

if (string || (((*text)[ptr] != ':') && ((*text)[ptr] != '?')))
continue;

if (((*text)[ptr] == ':') && ((*text)[ptr + 1] == ':'))
ptr += 2; /* skip '::' */
else
{
int len;
int buffersize = sizeof(int) * CHAR_BIT * 10 / 3; /* a rough guess of the
* size we need */
char *buffer,
*newcopy;

if (!(buffer = (char *) ecpg_alloc(buffersize, lineno)))
return false;

snprintf(buffer, buffersize, "$%d", counter++);

for (len = 1; (*text)[ptr + len] && isvarchar((*text)[ptr + len]); len++);
if (!(newcopy = (char *) ecpg_alloc(strlen(*text) -len + strlen(buffer) + 1, lineno)))
{
ecpg_free(buffer);
return false;
}

strncpy(newcopy, *text, ptr);
strcpy(newcopy + ptr, buffer);
strcat(newcopy, (*text) +ptr + len);

ecpg_free(*text);
ecpg_free(buffer);

*text = newcopy;

if ((*text)[ptr] == '\0') /* we reached the end */
ptr--; /* since we will (*text)[ptr]++ in the top
* level for loop */
}
}
return true;
}

static bool
prepare_common(int lineno, struct connection * con, const char *name, const char *variable)
{
struct statement *stmt;
struct prepared_statement *this;
PGresult *query;

/* allocate new statement */
this = (struct prepared_statement *) ecpg_alloc(sizeof(struct prepared_statement), lineno);
if (!this)
return false;

stmt = (struct statement *) ecpg_alloc(sizeof(struct statement), lineno);
if (!stmt)
{
ecpg_free(this);
return false;
}

/* create statement */
stmt->lineno = lineno;
stmt->connection = con;
stmt->command = ecpg_strdup(variable, lineno);
stmt->inlist = stmt->outlist = NULL;

/* if we have C variables in our statement replace them with '?' */
replace_variables(&(stmt->command), lineno);

/* add prepared statement to our list */
this->name = ecpg_strdup(name, lineno);
this->stmt = stmt;

/* and finally really prepare the statement */
query = PQprepare(stmt->connection->connection, name, stmt->command, 0, NULL);
if (!ecpg_check_PQresult(query, stmt->lineno, stmt->connection->connection, stmt->compat))
{
ecpg_free(stmt->command);
ecpg_free(this->name);
ecpg_free(this);
ecpg_free(stmt);
return false;
}

ecpg_log("prepare_common on line %d: name %s; query: \"%s\"\n", stmt->lineno, name, stmt->command);
PQclear(query);
this->prepared = true;

if (con->prep_stmts == NULL)
this->next = NULL;
else
this->next = con->prep_stmts;

con->prep_stmts = this;
return true;
}

/* handle the EXEC SQL PREPARE statement */
/* questionmarks is not needed but remains in there for the time being to not change the API */
bool
ECPGprepare(int lineno, const char *connection_name, const bool questionmarks, const char *name, const char *variable)
{
struct connection *con;
struct prepared_statement *this,
*prev;

(void) questionmarks; /* quiet the compiler */
con = ecpg_get_connection(connection_name);

if (!ecpg_init(con, connection_name, lineno))
return false;

/* check if we already have prepared this statement */
this = ecpg_find_prepared_statement(name, con, &prev);
if (this && !deallocate_one(lineno, ECPG_COMPAT_PGSQL, con, prev, this))
return false;

return prepare_common(lineno, con, name, variable);
}

struct prepared_statement *
ecpg_find_prepared_statement(const char *name,
struct connection * con, struct prepared_statement ** prev_)
{
struct prepared_statement *this,
*prev;

for (this = con->prep_stmts, prev = NULL; this != NULL; prev = this, this = this->next)
{
if (strcmp(this->name, name) == 0)
{
if (prev_)
*prev_ = prev;
return this;
}
}
return NULL;
}

static bool
deallocate_one(int lineno, enum COMPAT_MODE c, struct connection * con, struct prepared_statement * prev, struct prepared_statement * this)
{
bool r = false;

ecpg_log("deallocate_one on line %d: name %s\n", lineno, this->name);

/* first deallocate the statement in the backend */
if (this->prepared)
{
char *text;
PGresult *query;

text = (char *) ecpg_alloc(strlen("deallocate \"\" ") + strlen(this->name), this->stmt->lineno);

if (text)
{
sprintf(text, "deallocate \"%s\"", this->name);
query = PQexec(this->stmt->connection->connection, text);
ecpg_free(text);
if (ecpg_check_PQresult(query, lineno, this->stmt->connection->connection, this->stmt->compat))
{
PQclear(query);
r = true;
}
}
}

/*
* Just ignore all errors since we do not know the list of cursors we are
* allowed to free. We have to trust the software.
*/
if (!r && !INFORMIX_MODE(c))
{
ecpg_raise(lineno, ECPG_INVALID_STMT, ECPG_SQLSTATE_INVALID_SQL_STATEMENT_NAME, this->name);
return false;
}

/* okay, free all the resources */
ecpg_free(this->stmt->command);
ecpg_free(this->stmt);
ecpg_free(this->name);
if (prev != NULL)
prev->next = this->next;
else
con->prep_stmts = this->next;

ecpg_free(this);
return true;
}

/* handle the EXEC SQL DEALLOCATE PREPARE statement */
bool
ECPGdeallocate(int lineno, int c, const char *connection_name, const char *name)
{
struct connection *con;
struct prepared_statement *this,
*prev;

con = ecpg_get_connection(connection_name);

if (!ecpg_init(con, connection_name, lineno))
return false;

this = ecpg_find_prepared_statement(name, con, &prev);
if (this)
return deallocate_one(lineno, c, con, prev, this);

/* prepared statement is not found */
if (INFORMIX_MODE(c))
return true;
ecpg_raise(lineno, ECPG_INVALID_STMT, ECPG_SQLSTATE_INVALID_SQL_STATEMENT_NAME, name);
return false;
}

bool
ecpg_deallocate_all_conn(int lineno, enum COMPAT_MODE c, struct connection * con)
{
/* deallocate all prepared statements */
while (con->prep_stmts)
{
if (!deallocate_one(lineno, c, con, NULL, con->prep_stmts))
return false;
}

return true;
}

bool
ECPGdeallocate_all(int lineno, int compat, const char *connection_name)
{
return ecpg_deallocate_all_conn(lineno, compat, ecpg_get_connection(connection_name));
}

char *
ecpg_prepared(const char *name, struct connection * con)
{
struct prepared_statement *this;

this = ecpg_find_prepared_statement(name, con, NULL);
return this ? this->stmt->command : NULL;
}

/* return the prepared statement */
/* lineno is not used here, but kept in to not break API */
char *
ECPGprepared_statement(const char *connection_name, const char *name, int lineno)
{
(void) lineno; /* keep the compiler quiet */
return ecpg_prepared(name, ecpg_get_connection(connection_name));
}

/*
* hash a SQL statement - returns entry # of first entry in the bucket
*/
static int
HashStmt(const char *ecpgQuery)
{
int stmtIx,
bucketNo,
hashLeng,
stmtLeng;
long long hashVal,
rotVal;

stmtLeng = strlen(ecpgQuery);
hashLeng = 50; /* use 1st 50 characters of statement */
if (hashLeng > stmtLeng) /* if the statement isn't that long */
hashLeng = stmtLeng; /* use its actual length */

hashVal = 0;
for (stmtIx = 0; stmtIx < hashLeng; ++stmtIx)
{
hashVal = hashVal + (int) ecpgQuery[stmtIx];
hashVal = hashVal << 13;
rotVal = (hashVal & 0x1fff00000000LL) >> 32;
hashVal = (hashVal & 0xffffffffLL) | rotVal;
}

bucketNo = hashVal % stmtCacheNBuckets;
bucketNo += 1; /* don't use bucket # 0 */

return (bucketNo * stmtCacheEntPerBucket);
}

/*
* search the statement cache - search for entry with matching ECPG-format query
* Returns entry # in cache if found
* OR zero if not present (zero'th entry isn't used)
*/
static int
SearchStmtCache(const char *ecpgQuery)
{
int entNo,
entIx;

/* hash the statement */
entNo = HashStmt(ecpgQuery);

/* search the cache */
for (entIx = 0; entIx < stmtCacheEntPerBucket; ++entIx)
{
if (stmtCacheEntries[entNo].stmtID[0]) /* check if entry is in use */
{
if (strcmp(ecpgQuery, stmtCacheEntries[entNo].ecpgQuery) == 0)
break; /* found it */
}
++entNo; /* incr entry # */
}

/* if entry wasn't found - set entry # to zero */
if (entIx >= stmtCacheEntPerBucket)
entNo = 0;

return (entNo);
}

/*
* free an entry in the statement cache
* Returns entry # in cache used
* OR negative error code
*/
static int
ecpg_freeStmtCacheEntry(int lineno, int compat, int entNo) /* entry # to free */
{
stmtCacheEntry *entry;
struct connection *con;
struct prepared_statement *this,
*prev;

entry = &stmtCacheEntries[entNo];
if (!entry->stmtID[0]) /* return if the entry isn't in use */
return (0);

con = ecpg_get_connection(entry->connection);

/* free the 'prepared_statement' list entry */
this = ecpg_find_prepared_statement(entry->stmtID, con, &prev);
if (this && !deallocate_one(lineno, compat, con, prev, this))
return (-1);

entry->stmtID[0] = '\0';

/* free the memory used by the cache entry */
if (entry->ecpgQuery)
{
ecpg_free(entry->ecpgQuery);
entry->ecpgQuery = 0;
}

return (entNo);
}

/*
* add an entry to the statement cache
* returns entry # in cache used OR negative error code
*/
static int
AddStmtToCache(int lineno, /* line # of statement */
const char *stmtID, /* statement ID */
const char *connection, /* connection */
int compat, /* compatibility level */
const char *ecpgQuery) /* query */
{
int ix,
initEntNo,
luEntNo,
entNo;
stmtCacheEntry *entry;

/* hash the statement */
initEntNo = HashStmt(ecpgQuery);

/* search for an unused entry */
entNo = initEntNo; /* start with the initial entry # for the
* bucket */
luEntNo = initEntNo; /* use it as the initial 'least used' entry */
for (ix = 0; ix < stmtCacheEntPerBucket; ++ix)
{
entry = &stmtCacheEntries[entNo];
if (!entry->stmtID[0]) /* unused entry - use it */
break;
if (entry->execs < stmtCacheEntries[luEntNo].execs)
luEntNo = entNo; /* save new 'least used' entry */
++entNo; /* increment entry # */
}

/* if no unused entries were found - use the 'least used' entry found in the bucket */
if (ix >= stmtCacheEntPerBucket) /* if no unused entries were found */
entNo = luEntNo; /* re-use the 'least used' entry */

/* 'entNo' is the entry to use - make sure its free */
if (ecpg_freeStmtCacheEntry(lineno, compat, entNo) < 0)
return (-1);

/* add the query to the entry */
entry = &stmtCacheEntries[entNo];
entry->lineno = lineno;
entry->ecpgQuery = ecpg_strdup(ecpgQuery, lineno);
entry->connection = connection;
entry->execs = 0;
memcpy(entry->stmtID, stmtID, sizeof(entry->stmtID));

return (entNo);
}

/* handle cache and preparation of statements in auto-prepare mode */
bool
ecpg_auto_prepare(int lineno, const char *connection_name, const int compat, char **name, const char *query)
{
int entNo;

/* search the statement cache for this statement */
entNo = SearchStmtCache(query);

/* if not found - add the statement to the cache */
if (entNo)
{
char *stmtID;
struct connection *con;
struct prepared_statement *prep;

ecpg_log("ecpg_auto_prepare on line %d: statement found in cache; entry %d\n", lineno, entNo);

stmtID = stmtCacheEntries[entNo].stmtID;

con = ecpg_get_connection(connection_name);
prep = ecpg_find_prepared_statement(stmtID, con, NULL);
/* This prepared name doesn't exist on this connection. */
if (!prep && !prepare_common(lineno, con, stmtID, query))
return (false);

*name = ecpg_strdup(stmtID, lineno);
}
else
{
char stmtID[STMTID_SIZE];

ecpg_log("ecpg_auto_prepare on line %d: statement not in cache; inserting\n", lineno);

/* generate a statement ID */
sprintf(stmtID, "ecpg%d", nextStmtID++);

if (!ECPGprepare(lineno, connection_name, 0, stmtID, query))
return (false);
if (AddStmtToCache(lineno, stmtID, connection_name, compat, query) < 0)
return (false);

*name = ecpg_strdup(stmtID, lineno);
}

/* increase usage counter */
stmtCacheEntries[entNo].execs++;

return (true);
}
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