src/rio.c

   1 /* rio.c is a simple stream-oriented I/O abstraction that provides an interface
   2  * to write code that can consume/produce data using different concrete input
   3  * and output devices. For instance the same rdb.c code using the rio abstraction
   4  * can be used to read and write the RDB format using in-memory buffers or files.
   5  *
   6  * A rio object provides the following methods:
   7  *  read: read from stream.
   8  *  write: write to stream.
   9  *  tell: get the current offset.
  10  *
  11  * It is also possible to set a 'checksum' method that is used by rio.c in order
  12  * to compute a checksum of the data written or read, or to query the rio object
  13  * for the current checksum. */
  14
  15 #include "fmacros.h"
  16 #include <string.h>
  17 #include <stdio.h>
  18 #include "rio.h"
  19 #include "util.h"
  20
  21 /* Returns 1 or 0 for success/failure. */
  22 static size_t rioBufferWrite(rio *r, const void *buf, size_t len) {
  23     r->io.buffer.ptr = sdscatlen(r->io.buffer.ptr,(char*)buf,len);
  24     r->io.buffer.pos += len;
  25     return 1;
  26 }
  27
  28 /* Returns 1 or 0 for success/failure. */
  29 static size_t rioBufferRead(rio *r, void *buf, size_t len) {
  30     if (sdslen(r->io.buffer.ptr)-r->io.buffer.pos < len)
  31         return 0; /* not enough buffer to return len bytes. */
  32     memcpy(buf,r->io.buffer.ptr+r->io.buffer.pos,len);
  33     r->io.buffer.pos += len;
  34     return 1;
  35 }
  36
  37 /* Returns read/write position in buffer. */
  38 static off_t rioBufferTell(rio *r) {
  39     return r->io.buffer.pos;
  40 }
  41
  42 /* Returns 1 or 0 for success/failure. */
  43 static size_t rioFileWrite(rio *r, const void *buf, size_t len) {
  44     return fwrite(buf,len,1,r->io.file.fp);
  45 }
  46
  47 /* Returns 1 or 0 for success/failure. */
  48 static size_t rioFileRead(rio *r, void *buf, size_t len) {
  49     return fread(buf,len,1,r->io.file.fp);
  50 }
  51
  52 /* Returns read/write position in file. */
  53 static off_t rioFileTell(rio *r) {
  54     return ftello(r->io.file.fp);
  55 }
  56
  57 static const rio rioBufferIO = {
  58     rioBufferRead,
  59     rioBufferWrite,
  60     rioBufferTell,
  61     NULL,           /* update_checksum */
  62     0,              /* current checksum */
  63     { { NULL, 0 } } /* union for io-specific vars */
  64 };
  65
  66 static const rio rioFileIO = {
  67     rioFileRead,
  68     rioFileWrite,
  69     rioFileTell,
  70     NULL,           /* update_checksum */
  71     0,              /* current checksum */
  72     { { NULL, 0 } } /* union for io-specific vars */
  73 };
  74
  75 void rioInitWithFile(rio *r, FILE *fp) {
  76     *r = rioFileIO;
  77     r->io.file.fp = fp;
  78 }
  79
  80 void rioInitWithBuffer(rio *r, sds s) {
  81     *r = rioBufferIO;
  82     r->io.buffer.ptr = s;
  83     r->io.buffer.pos = 0;
  84 }
  85
  86 /* This function can be installed both in memory and file streams when checksum
  87  * computation is needed. */
  88 void rioGenericUpdateChecksum(rio *r, const void *buf, size_t len) {
  89     r->checksum = crc64(r->checksum,buf,len);
  90 }
  91
  92 /* ------------------------------ Higher level interface ---------------------------
  93  * The following higher level functions use lower level rio.c functions to help
  94  * generating the Redis protocol for the Append Only File. */
  95
  96 /* Write multi bulk count in the format: "*<count>\r\n". */
  97 size_t rioWriteBulkCount(rio *r, char prefix, int count) {
  98     char cbuf[128];
  99     int clen;
 100
 101     cbuf[0] = prefix;
 102     clen = 1+ll2string(cbuf+1,sizeof(cbuf)-1,count);
 103     cbuf[clen++] = '\r';
 104     cbuf[clen++] = '\n';
 105     if (rioWrite(r,cbuf,clen) == 0) return 0;
 106     return clen;
 107 }
 108
 109 /* Write binary-safe string in the format: "$<count>\r\n<payload>\r\n". */
 110 size_t rioWriteBulkString(rio *r, const char *buf, size_t len) {
 111     size_t nwritten;
 112
 113     if ((nwritten = rioWriteBulkCount(r,'$',len)) == 0) return 0;
 114     if (len > 0 && rioWrite(r,buf,len) == 0) return 0;
 115     if (rioWrite(r,"\r\n",2) == 0) return 0;
 116     return nwritten+len+2;
 117 }
 118
 119 /* Write a long long value in format: "$<count>\r\n<payload>\r\n". */
 120 size_t rioWriteBulkLongLong(rio *r, long long l) {
 121     char lbuf[32];
 122     unsigned int llen;
 123
 124     llen = ll2string(lbuf,sizeof(lbuf),l);
 125     return rioWriteBulkString(r,lbuf,llen);
 126 }
 127
 128 /* Write a double value in the format: "$<count>\r\n<payload>\r\n" */
 129 size_t rioWriteBulkDouble(rio *r, double d) {
 130     char dbuf[128];
 131     unsigned int dlen;
 132
 133     dlen = snprintf(dbuf,sizeof(dbuf),"%.17g",d);
 134     return rioWriteBulkString(r,dbuf,dlen);
 135 }