diff options
Diffstat (limited to 'reference/C/CONTRIB/SNIP/strucfil.c')
| -rwxr-xr-x | reference/C/CONTRIB/SNIP/strucfil.c | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/reference/C/CONTRIB/SNIP/strucfil.c b/reference/C/CONTRIB/SNIP/strucfil.c new file mode 100755 index 0000000..a0b6522 --- /dev/null +++ b/reference/C/CONTRIB/SNIP/strucfil.c @@ -0,0 +1,190 @@ +/*******************************************************************
+ * Generic structure <> disk file manipulations. These functions
+ * form a basic template for reading and writing structures to a
+ * sequential file. This template is probably most useful for files
+ * with 500 or less records and eliminates the need for a more
+ * elaborate file handler such as C-Tree, DB-Vista, Mix etc.
+ * Routines to put data in the struct is out of scope here.
+ * Written by Lynn Nash 8/28/91 and donated to the public domain.
+ */
+#include <io.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#ifndef ERROR
+#define ERROR -1
+#define OK 0
+#endif
+
+#ifndef TRUE
+#define TRUE 1
+#define FALSE !TRUE
+#endif
+
+/* make sure the record structure is byte aligned */
+
+#if defined(__TURBOC__)
+ #pragma option -a-
+#elif defined(__ZTC__)
+ #pragma ZTC align 1
+#else /* MSC/QC/WATCOM/METAWARE */
+ #pragma pack(1)
+#endif
+
+static struct blackbook {
+ int delete_flag; /* 0 = active -1 = deleted */
+ int recordnum; /* a sequential number in the file */
+ /* The data fields in asciiz. */
+ char firstname[11];
+ char lastname[16];
+ char addr[26];
+ char city[16];
+ char state[3];
+ char zip[10];
+ char phone[11];
+} rec, oldrec; /* 97 byte record * 2 */
+
+#pragma pack()
+
+/*-------------------- general globals ---------------------*/
+
+static long cur_rec = 0; /* the current record number */
+static FILE *fsptr = NULL; /* fixed record data file pointer */
+
+/* if file exists open in read/write mode else create file */
+
+FILE * open_file(char *filename)
+{
+ if (access(filename, 0) == 0)
+ fsptr = fopen(filename, "rb+");
+ else fsptr = fopen(filename, "wb+");
+ return fsptr; /* return the file pointer */
+}
+
+/* add new records to the data file */
+
+int datadd(void)
+{
+ if (fsptr)
+ {
+ if (fseek(fsptr, 0L, SEEK_END) != 0)
+ return ERROR; /* seek failure */
+ rec.delete_flag = 0; /* active record tag */
+ rec.recordnum = (int) (ftell(fsptr) /
+ (long) sizeof(struct blackbook));
+ if (fwrite(&rec, sizeof(struct blackbook), 1, fsptr) != 1)
+ {
+ return ERROR; /* write error */
+ }
+ else
+ {
+ /* put your clean up code here */
+ return OK;
+ }
+ }
+ return ERROR;
+}
+
+/* tag the last record read in the file as deleted */
+
+int data_delete(void)
+{
+ if (fsptr)
+ {
+ if (fseek(fsptr, (long) sizeof(struct blackbook) * -1L,
+ SEEK_CUR) != 0)
+ {
+ return ERROR;
+ }
+ rec.delete_flag = -1; /* tag the record as deleted */
+ if (fwrite(&rec, sizeof(struct blackbook), 1, fsptr) != 1)
+ return ERROR;
+ else return OK;
+ }
+ return ERROR;
+}
+
+/* read a random structure. If successful the global cur_rec will
+ * contain the number of the last record read & it can be compared
+ * to the number in the struct as a double check (belt & suspenders)
+ */
+
+int data_read(long recnum)
+{
+ if (fseek(fsptr, (long) sizeof(struct blackbook) * recnum,
+ SEEK_SET) != 0)
+ {
+ return ERROR;
+ }
+ cur_rec = recnum; /* keep tabs on record pointer in global */
+
+ /* now read the record into save struct*/
+
+ if (fread(&oldrec, sizeof(struct blackbook), 1, fsptr) != 1)
+ {
+ return ERROR;
+ }
+ else /* copy save struct to edit struct */
+ {
+ memcpy(&rec, &oldrec, sizeof(struct blackbook));
+ return OK;
+ }
+}
+
+/* rewrite the last read record back to disk */
+
+int data_update(void)
+{
+ if (memcmp(&rec, &oldrec, sizeof(struct blackbook)) == 0)
+ return TRUE; /* no update needed */
+
+ /* back up one record before writing */
+
+ if (fseek(fsptr, (long) sizeof(struct blackbook) * -1L,
+ SEEK_CUR) != 0)
+ {
+ return ERROR; /* seek error */
+ }
+
+ /* now write the record */
+
+ if (fwrite(&rec, sizeof(struct blackbook), 1, fsptr) != 1)
+ return ERROR; /* write error */
+ return OK;
+}
+
+/* get the next valid record in the file */
+
+int read_forward(void)
+{
+ do
+ {
+ cur_rec++; /* upcount the record number */
+ if (data_read(cur_rec) != 0)
+ {
+ cur_rec--; /* decrement the record number */
+ return ERROR;
+ }
+ } while (oldrec.delete_flag != 0); /* record read was deleted */
+ return OK;
+}
+
+/* get the previous valid record in the file */
+
+int read_backward(void)
+{
+ do
+ {
+ cur_rec--; /* decrement the record number */
+ if (cur_rec >= 0)
+ {
+ if ( data_read(cur_rec) != 0 )
+ {
+ cur_rec++; /* increment the record number */
+ return ERROR;
+ }
+ }
+ } while (oldrec.delete_flag != 0); /* record read was deleted */
+ return OK;
+}
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