1RFIO_PRESEEK(3) Rfio Library Functions
2RFIO_PRESEEK(3)
3[1mNAME[0m
7 rfio_preseek ‐ prefetch chunks of data from a file
8[1mSYNOPSIS[0m
10 [1m#include <sys/types.h>[0m
11 [1m#include "rfio_api.h"[0m
12 [1mint rfio_preseek (int [4m[22ms[24m[1m, const struct
14iovec *[4m[22miov[24m[1m, int [4m[22miovnb[24m[1m);[0m
15 Under Linux, for large files:
17 [1m#define _LARGEFILE64_SOURCE[0m
18 [1m#include <sys/types.h>[0m
19 [1m#include "rfio_api.h"[0m
20 [1mint rfio_preseek64 (int [4m[22ms[24m[1m, const struct
22iovec64 *[4m[22miov[24m[1m, int [4m[22miovnb[24m[1m);[0m
23 For large files, under other systems:
25 [1m#include <sys/types.h>[0m
26 [1m#include "rfio_api.h"[0m
27 [1mint rfio_preseek64 (int [4m[22ms[24m[1m, const struct
29iovec64 *[4m[22miov[24m[1m, int [4m[22miovnb[24m[1m);[0m
30[1mDESCRIPTION[0m
32 [1mrfio_preseek [22mprefetches chunks of data at given
33offsets into an inter‐
34 nal buffer (on the client side), using the descriptor [1ms
35[22mgenerated by a
36 previous [1mrfio_open[22m. The actual offset values and
37the lengths are given
38 in the array of structures [1miov[22m. The number of
39chunks is specified by
40 [1miovnb[22m.
41 [1mrfio_preseek64 [22mdoes the prefetch for large
43files, using an array of
44 structures of type [1miovec64 [22mrather than an array of
45[1miovec[22m.
46 [1mRFIO_READOPT [22mmust be set to RFIO_READBUF, which is
48the default. The
49 default internal buffer size is 128 kB, but the buffer
50size can be set
51 with an entry RFIO IOBUFSIZE in [1mshift.conf[22m. Then
52[1mrfio_read [22mgets the
53 data from that buffer.
54[1mEXAMPLES[0m
56 /* tpreseek ‐ write NBRECORDS_TOWRITE records and
57 read back NBRECORDS_TOREAD using the rfio_pre‐
58seek function */
59 #include <fcntl.h>
61 #include <stdio.h>
62 #if defined(_WIN32)
63 #include <winsock2.h>
64 #endif
65 #include "rfio_api.h"
66 #define NBRECORDS_TOREAD 5
67 #define NBRECORDS_TOWRITE 10
68 main(argc, argv)
70 int argc;
71 char **argv;
72 {
73 char buf[65536];
74 int errflg = 0;
75 int fd;
76 int i;
77 struct iovec iov[NBRECORDS_TOREAD];
78 int iovnb = NBRECORDS_TOREAD;
79 int j;
80 static int lengths[NBRECORDS_TOWRITE] = {4096, 32768,
8116384, 8192,
82 65536, 32768, 16384, 4096, 65536,
838192};
84 static int records_toread[NBRECORDS_TOREAD] = {2, 4,
855, 8, 9};
86 #if defined(_WIN32)
87 WSADATA wsadata;
88 #endif
89 if (argc != 2) {
91 fprintf (stderr, "usage: tpreseek pathname0);
92 exit (1);
93 }
94 #if defined(_WIN32)
95 if (WSAStartup (MAKEWORD (2, 0), &wsadata)) {
96 fprintf (stderr, "WSAStartup unsuccessful0);
97 exit (2);
98 }
99 #endif
100 while (! errflg) {
101 /* Write variable length records.
103 * Each record is filled with the record index
104 */
105 if ((fd = rfio_open (argv[1],
107 O_WRONLY|O_CREAT|O_TRUNC, 0644)) < 0) {
108 rfio_perror ("rfio_open");
109 errflg++;
110 break;
111 }
112 for (j = 0; j < NBRECORDS_TOWRITE; j++) {
113 for (i = 0; i < lengths[j]; i++)
114 buf[i] = j;
115 if (rfio_write (fd, buf, lengths[j]) < 0) {
116 rfio_perror ("rfio_write");
117 errflg++;
118 break;
119 }
120 }
121 (void)rfio_close (fd);
122 if (errflg) break;
123 /* Prefetch a few records: the actual offsets
125and lengths
126 * of the records is set in the array of iov
127structures
128 */
129 if ((fd = rfio_open (argv[1], O_RDONLY)) < 0) {
131 rfio_perror ("rfio_open");
132 errflg++;
133 break;
134 }
135 for (j = 0; j < NBRECORDS_TOREAD; j++) {
136 /* compute record offset */
137 iov[j].iov_base = 0;
138 for (i = 0; i < records_toread[j]; i++)
139 iov[j].iov_base = (char *)
140iov[j].iov_base +
141 lengths[i];
142 /* set length */
143 iov[j].iov_len = lengths[records_tore‐
144ad[j]];
145 }
146 if (rfio_preseek (fd, iov, iovnb) < 0) {
147 rfio_perror ("rfio_preseek");
148 errflg++;
149 break;
150 }
151 /* Read back the records and check their cpn‐
153tents */
154 for (j = 0; j < NBRECORDS_TOREAD; j++) {
156 if (rfio_lseek (fd, (off_t)
157iov[j].iov_base,
158 SEEK_SET) < 0) {
159 rfio_perror ("rfio_lseek");
160 errflg++;
161 break;
162 }
163 if (rfio_read (fd, buf, iov[j].iov_len) <
1640) {
165 rfio_perror ("rfio_read");
166 errflg++;
167 break;
168 }
169 for (i = 0; i < iov[j].iov_len; i++) {
170 if (buf[i] != records_toread[j]) {
171 fprintf (stderr,
172 "incorrect data read, record
173%d0,
174 records_toread[j]);
175 errflg++;
176 break;
177 }
178 }
179 if (errflg) break;
180 }
181 (void) rfio_close (fd);
182 break;
183 }
184 if (rfio_unlink (argv[1]) < 0) {
185 rfio_perror ("rfio_unlink");
186 errflg++;
187 }
188 #if defined(_WIN32)
189 WSACleanup();
190 #endif
191 exit (errflg ? 1 : 0);
192 }
193[1mRETURN VALUE[0m
195 This routine returns 0 if the operation was successful
196or ‐1 if the
197 operation failed. In the latter case, [1mserrno [22mis set
198appropriately.
199[1mERRORS[0m
201 [1mEBADF [4m[22ms[24m is not a valid descriptor.
202 [1mEINVAL [22mRFIO_READOPT is not set to RFIO_READ‐
204BUF.
205 [1mSENOSHOST [22mHost unknown.
207 [1mSENOSSERV [22mService unknown.
209 [1mSETIMEDOUT [22mTimed out.
211 [1mSEBADVERSION [22mVersion ID mismatch.
213 [1mSECONNDROP [22mConnection closed by remote end.
215 [1mSECOMERR [22mCommunication error.
217 [1mSENORCODE [22mHost did not return error number.
219[1mSEE ALSO[0m
221 [1mrfio_lseek(3)[22m, [1mrfio_open(3)[22m, [1mr‐
222fio_read(3)[0m
223[1mAUTHOR[0m
225 [1mLCG Grid Deployment [22mTeam
226LCG $Date: 2005/03/31 13:13:03 $
230RFIO_PRESEEK(3)
231