FreeTDS API: src/dblib/buffering.h Source File

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# buffering.h

    00001 typedef struct dblib_buffer_row {
    00003         TDSRESULTINFO *resinfo;
    00005         unsigned char *row_data;
    00007         DBINT row;
    00009         TDS_INT *sizes;
    00010 } DBLIB_BUFFER_ROW;
    00011
    00012 static void buffer_struct_print(const DBPROC_ROWBUF *buf);
    00013 static int buffer_save_row(DBPROCESS *dbproc);
    00014 static DBLIB_BUFFER_ROW* buffer_row_address(const DBPROC_ROWBUF * buf, int idx);
    00015
    00045 static int
    00046 buffer_count(const DBPROC_ROWBUF *buf)
    00047 {
    00048         return (buf->head > buf->tail) ?
    00049                 buf->head - buf->tail :                         /* |...TddddH....| */
    00050                 buf->capacity - (buf->tail - buf->head);        /* |ddddH....Tddd| */
    00051 }
    00052
    00056 static int
    00057 buffer_is_full(const DBPROC_ROWBUF *buf)
    00058 {
    00059         return buf->capacity == buffer_count(buf) && buf->capacity > 1;
    00060 }
    00061
    00062 static int
    00063 buffer_index_valid(const DBPROC_ROWBUF *buf, int idx)
    00064 {
    00065         if (buf->tail <= buf->head)
    00066                 if (buf->head <= idx && idx <= buf->tail)
    00067                         return 1;
    00068
    00069         if (0 <= idx && idx <= buf->head)
    00070                 return 1;
    00071
    00072         if (buf->tail <= idx && idx < buf->capacity)
    00073                 return 1;
    00074 #if 0
    00075         printf("buffer_index_valid: idx = %d\n", idx);
    00076         buffer_struct_print(buf);
    00077 #endif
    00078         return 0;
    00079 }
    00080
    00081 static void
    00082 buffer_free_row(DBLIB_BUFFER_ROW *row)
    00083 {
    00084         if (row->sizes)
    00085                 TDS_ZERO_FREE(row->sizes);
    00086         if (row->row_data) {
    00087                 tds_free_row(row->resinfo, row->row_data);
    00088                 row->row_data = NULL;
    00089         }
    00090         tds_free_results(row->resinfo);
    00091         row->resinfo = NULL;
    00092 }
    00093
    00094 /*
    00095  * Buffer is freed at slightly odd points, whenever
    00096  * capacity changes:
    00097  *
    00098  * 1. When setting capacity, to release prior buffer.
    00099  * 2. By dbresults.  When called the second time, it has to
    00100  * release prior storage because the new resultset will have
    00101  * a different width.
    00102  * 3. By dbclose(), else open/close/open would leak.
    00103  */
    00104 static void
    00105 buffer_free(DBPROC_ROWBUF *buf)
    00106 {
    00107         if (buf->rows != NULL) {
    00108                 int i;
    00109                 for (i = 0; i < buf->capacity; ++i)
    00110                         buffer_free_row(&buf->rows[i]);
    00111                 TDS_ZERO_FREE(buf->rows);
    00112         }
    00113 }
    00114
    00115 /*
    00116  * When no rows are currently buffered (and the buffer is allocated)
    00117  * set the indices to their initial postions.
    00118  */
    00119 static void
    00120 buffer_reset(DBPROC_ROWBUF *buf)
    00121 {
    00122         buf->head = 0;
    00123         buf->current = buf->tail = buf->capacity;
    00124 }
    00125
    00126 static int
    00127 buffer_idx_increment(const DBPROC_ROWBUF *buf, int idx)
    00128 {
    00129         if (++idx >= buf->capacity) {
    00130                 idx = 0;
    00131         }
    00132         return idx;
    00133 }
    00134
    00139 static DBLIB_BUFFER_ROW*
    00140 buffer_row_address(const DBPROC_ROWBUF * buf, int idx)
    00141 {
    00142         if (!(idx >= 0 && idx < buf->capacity)) {
    00143                 printf("idx is %d:\n", idx);
    00144                 buffer_struct_print(buf);
    00145                 assert(idx >= 0);
    00146                 assert(idx < buf->capacity);
    00147         }
    00148
    00149         return &(buf->rows[idx]);
    00150 }
    00151
    00155 static DBINT
    00156 buffer_idx2row(const DBPROC_ROWBUF *buf, int idx)
    00157 {
    00158         return buffer_row_address(buf, idx)->row;
    00159 }
    00160
    00164 static int
    00165 buffer_row2idx(const DBPROC_ROWBUF *buf, int row_number)
    00166 {
    00167         int i, ii, idx = -1;
    00168
    00169         if (buf->tail == buf->capacity) {
    00170                 assert (buf->head == 0);
    00171                 return -1;      /* no rows buffered */
    00172         }
    00173
    00174         /*
    00175          * March through the buffers from tail to head, stop if we find our row.
    00176          * A full queue is indicated by tail == head (which means we can't write).
    00177          */
    00178         for (ii=0, i = buf->tail; i != buf->head || ii == 0; i = buffer_idx_increment(buf, i)) {
    00179                 if( buffer_idx2row(buf, i) == row_number) {
    00180                         idx = i;
    00181                         break;
    00182                 }
    00183                 assert(ii++ < buf->capacity); /* prevent infinite loop */
    00184         }
    00185
    00186         return idx;
    00187 }
    00188
    00194 static void
    00195 buffer_delete_rows(DBPROC_ROWBUF * buf, int count)
    00196 {
    00197         int i;
    00198
    00199         if (count < 0 || count > buffer_count(buf)) {
    00200                 count = buffer_count(buf);
    00201         }
    00202
    00203         for (i=0; i < count; i++) {
    00204                 if (buf->tail < buf->capacity)
    00205                         buffer_free_row(&buf->rows[i]);
    00206                 buf->tail = buffer_idx_increment(buf, buf->tail);
    00207                 /*
    00208                  * If deleting rows from the buffer catches the tail to the head,
    00209                  * return to the initial postion.  Otherwise, it will look full.
    00210                  */
    00211                 if (buf->tail == buf->head) {
    00212                         buffer_reset(buf);
    00213                         break;
    00214                 }
    00215         }
    00216 #if 0
    00217         buffer_struct_print(buf);
    00218 #endif
    00219 }
    00220
    00221 static void
    00222 buffer_transfer_bound_data(DBPROC_ROWBUF *buf, TDS_INT res_type, TDS_INT compute_id, DBPROCESS * dbproc, int idx)
    00223 {
    00224
    00225         int i;
    00226         TDSCOLUMN *curcol;
    00227         TDSRESULTINFO *resinfo;
    00228         int srctype;
    00229         BYTE *src;
    00230         int desttype;
    00231         const DBLIB_BUFFER_ROW *row;
    00232
    00233         assert(buffer_index_valid(buf, idx));
    00234
    00235         row = buffer_row_address(buf, idx);
    00236         assert(row->resinfo);
    00237         resinfo = row->resinfo;
    00238
    00239         for (i = 0; i < resinfo->num_cols; i++) {
    00240                 DBINT srclen;
    00241
    00242                 curcol = resinfo->columns[i];
    00243                 if (row->sizes)
    00244                         curcol->column_cur_size = row->sizes[i];
    00245
    00246                 if (curcol->column_nullbind) {
    00247                         if (curcol->column_cur_size < 0) {
    00248                                 *(DBINT *)(curcol->column_nullbind) = -1;
    00249                         } else {
    00250                                 *(DBINT *)(curcol->column_nullbind) = 0;
    00251                         }
    00252                 }
    00253                 if (!curcol->column_varaddr)
    00254                         continue;
    00255
    00256                 src = (row->row_data ? row->row_data : row->resinfo->current_row) + curcol->column_offset;
    00257                 srclen = curcol->column_cur_size;
    00258                 if (is_blob_type(curcol->column_type)) {
    00259                         src = (BYTE *) ((TDSBLOB *) src)->textvalue;
    00260                 }
    00261                 desttype = _db_get_server_type(curcol->column_bindtype);
    00262                 srctype = tds_get_conversion_type(curcol->column_type, curcol->column_size);
    00263
    00264                 if (srclen < 0) {
    00265                         _set_null_value((BYTE *) curcol->column_varaddr, desttype, curcol->column_bindlen);
    00266                 } else {
    00267                         copy_data_to_host_var(dbproc, srctype, src, srclen, desttype,
    00268                                                 (BYTE *) curcol->column_varaddr,  curcol->column_bindlen,
    00269                                                          curcol->column_bindtype, curcol->column_nullbind);
    00270                 }
    00271         }
    00272
    00273         /*
    00274          * This function always bumps current.  Usually, it's called
    00275          * by dbnextrow(), so bumping current is a pretty obvious choice.
    00276          * It can also be called by dbgetrow(), but that function also
    00277          * causes the bump.  If you call dbgetrow() for row N, a subsequent
    00278          * call to dbnextrow() yields N+1.
    00279          */
    00280         buf->current = buffer_idx_increment(buf, buf->current);
    00281
    00282 }       /* end buffer_transfer_bound_data()  */
    00283
    00284 static void
    00285 buffer_struct_print(const DBPROC_ROWBUF *buf)
    00286 {
    00287         assert(buf);
    00288
    00289         printf("\t%d rows in buffer\n",         buffer_count(buf));
    00290
    00291         printf("\thead = %d\t",                 buf->head);
    00292         printf("\ttail = %d\t",                 buf->tail);
    00293         printf("\tcurrent = %d\n",              buf->current);
    00294         printf("\tcapacity = %d\t",             buf->capacity);
    00295         printf("\thead row number = %d\n",      buf->received);
    00296 }
    00297
    00298 /* * * Functions called only by public db-lib API take DBPROCESS* * */
    00299
    00316 static int
    00317 buffer_current_index(const DBPROCESS *dbproc)
    00318 {
    00319         const DBPROC_ROWBUF *buf = &dbproc->row_buf;
    00320 #if 0
    00321         buffer_struct_print(buf);
    00322 #endif
    00323         if (buf->capacity <= 1) /* no buffering */
    00324                 return -1;
    00325         if (buf->current == buf->head || buf->current == buf->capacity)
    00326                 return -1;
    00327
    00328         assert(buf->current >= 0);
    00329         assert(buf->current < buf->capacity);
    00330
    00331         if( buf->tail < buf->head) {
    00332                 assert(buf->tail < buf->current);
    00333                 assert(buf->current < buf->head);
    00334         } else {
    00335                 if (buf->current > buf->head)
    00336                         assert(buf->current > buf->tail);
    00337         }
    00338         return buf->current;
    00339 }
    00340
    00341 /*
    00342  * Normally called by dbsetopt() to prepare for buffering
    00343  * Called with nrows == 0 by dbopen to safely set buf->rows to NULL.
    00344  */
    00345 static void
    00346 buffer_set_capacity(DBPROCESS *dbproc, int nrows)
    00347 {
    00348         DBPROC_ROWBUF *buf = &dbproc->row_buf;
    00349
    00350         buffer_free(buf);
    00351
    00352         memset(buf, 0, sizeof(DBPROC_ROWBUF));
    00353
    00354         if (0 == nrows) {
    00355                 buf->capacity = 1;
    00356                 return;
    00357         }
    00358
    00359         assert(0 < nrows);
    00360
    00361         buf->capacity = nrows;
    00362 }
    00363
    00364 /*
    00365  * Called only by dbresults(); capacity must be >= 1.
    00366  * Sybase's documents say dbresults() cannot return FAIL if the prior calls worked,
    00367  * which is a little strange, because (for FreeTDS, at least), dbresults
    00368  * is when we learn about the result set's width.  Without that information, we
    00369  * can't allocate memory for the buffer.  But if we *fail* to allocate memory,
    00370  * we're not to communicate it back to the caller?
    00371  */
    00372 static void
    00373 buffer_alloc(DBPROCESS *dbproc)
    00374 {
    00375         DBPROC_ROWBUF *buf = &dbproc->row_buf;
    00376
    00377         /* Call this function only after setting capacity. */
    00378
    00379         assert(buf);
    00380         assert(buf->capacity > 0);
    00381         assert(buf->rows == NULL);
    00382
    00383         buf->rows = (DBLIB_BUFFER_ROW *) calloc(buf->capacity, sizeof(DBLIB_BUFFER_ROW));
    00384
    00385         assert(buf->rows);
    00386
    00387         buffer_reset(buf);
    00388
    00389         buf->received = 0;
    00390 }
    00391
    00396 static int
    00397 buffer_add_row(DBPROCESS *dbproc, TDSRESULTINFO *resinfo)
    00398 {
    00399         DBPROC_ROWBUF *buf = &dbproc->row_buf;
    00400         DBLIB_BUFFER_ROW *row;
    00401         int i;
    00402
    00403         assert(buf->capacity >= 0);
    00404
    00405         if (buffer_is_full(buf))
    00406                 return -1;
    00407
    00408         /* initial condition is head == 0 and tail == capacity */
    00409         if (buf->tail == buf->capacity) {
    00410                 /* bumping this tail will set it to zero */
    00411                 assert(buf->head == 0);
    00412                 buf->tail = buffer_idx_increment(buf, buf->tail);
    00413         }
    00414
    00415         row = buffer_row_address(buf, buf->head);
    00416
    00417         /* bump the row number, write it, and move the data to head */
    00418         if (row->resinfo) {
    00419                 tds_free_row(row->resinfo, row->row_data);
    00420                 tds_free_results(row->resinfo);
    00421         }
    00422         row->row = ++buf->received;
    00423         ++resinfo->ref_count;
    00424         row->resinfo = resinfo;
    00425         row->row_data = NULL;
    00426         if (row->sizes)
    00427                 free(row->sizes);
    00428         row->sizes = (TDS_INT *) calloc(resinfo->num_cols, sizeof(TDS_INT));
    00429         for (i = 0; i < resinfo->num_cols; ++i)
    00430                 row->sizes[i] = resinfo->columns[i]->column_cur_size;
    00431
    00432         /* update current, bump the head */
    00433         buf->current = buf->head;
    00434         buf->head = buffer_idx_increment(buf, buf->head);
    00435
    00436         return buf->current;
    00437 }
    00438
    00439 static int
    00440 buffer_save_row(DBPROCESS *dbproc)
    00441 {
    00442         DBPROC_ROWBUF *buf = &dbproc->row_buf;
    00443         DBLIB_BUFFER_ROW *row;
    00444         int idx = buf->head - 1;
    00445
    00446         if (buf->capacity <= 1)
    00447                 return SUCCEED;
    00448
    00449         if (idx < 0)
    00450                 idx = buf->capacity - 1;
    00451         if (idx >= 0 && idx < buf->capacity) {
    00452                 row = &buf->rows[idx];
    00453
    00454                 if (row->resinfo && !row->row_data) {
    00455                         row->row_data = row->resinfo->current_row;
    00456                         row->resinfo->current_row = tds_alloc_row(row->resinfo);
    00457                 }
    00458         }
    00459
    00460         return SUCCEED;
    00461 }
    00462