Hadoop通过ｃ语言API访问hdfs

  1 #include <stdio.h>
  2 
  3 #include <stdlib.h>
  4 
  5 #include <string.h>
  6 
  7 #include "hdfs.h"
  8 
  9  
 10 
 11 int main(int argc, char **argv)
 12 
 13 {
 14 
 15     /*
 16 
 17      * Connection to hdfs.
 18 
 19      */
 20 
 21     hdfsFS fs = hdfsConnect("127.0.0.1", 9000);
 22 
 23     if(!fs)
 24 
 25     {
 26 
 27         fprintf(stderr, "Failed to connect to hdfs.\n");
 28 
 29         exit(-1);
 30 
 31     }
 32 
 33     /*
 34 
 35      * Create and open a file in hdfs.
 36 
 37      */
 38 
 39     const char* writePath = "/user/root/output/testfile.txt";
 40 
 41     hdfsFile writeFile = hdfsOpenFile(fs, writePath, O_WRONLY|O_CREAT, 0, 0, 0);
 42 
 43     if(!writeFile)
 44 
 45     {
 46 
 47         fprintf(stderr, "Failed to open %s for writing!\n", writePath);
 48 
 49         exit(-1);
 50 
 51     }
 52 
 53     /*
 54 
 55      * Write data to the file.
 56 
 57      */
 58 
 59     const char* buffer = "Hello, World!";
 60 
 61     tSize num_written_bytes = hdfsWrite(fs, writeFile, (void*)buffer, strlen(buffer)+1);
 62 
 63  
 64 
 65     /*
 66 
 67      * Flush buffer.
 68 
 69      */
 70 
 71     if (hdfsFlush(fs, writeFile))
 72 
 73     {
 74 
 75         fprintf(stderr, "Failed to ‘flush‘ %s\n", writePath);
 76 
 77         exit(-1);
 78 
 79     }
 80 
 81  
 82 
 83     /*
 84 
 85      * Close the file.
 86 
 87      */
 88 
 89     hdfsCloseFile(fs, writeFile);
 90 
 91  
 92 
 93     unsigned bufferSize=1024;
 94 
 95     const char* readPath = "/user/root/output/testfile.txt";
 96 
 97     hdfsFile readFile = hdfsOpenFile(fs, readPath, O_RDONLY, bufferSize, 0, 0);
 98 
 99     if (!readFile) {
100 
101         fprintf(stderr,"couldn‘t open file %s for reading\n",readPath);
102 
103         exit(-2);
104 
105     }
106 
107     // data to be written to the file
108 
109     char* rbuffer = (char*)malloc(sizeof(char) * (bufferSize+1));
110 
111     if(rbuffer == NULL) {
112 
113         return -2;
114 
115     }
116 
117  
118 
119     // read from the file
120 
121     tSize curSize = bufferSize;
122 
123     for (; curSize == bufferSize;) {
124 
125         curSize = hdfsRead(fs, readFile, (void*)rbuffer, curSize);
126 
127         rbuffer[curSize]=‘\0‘;
128 
129         fprintf(stdout, "read ‘%s‘ from file!\n", rbuffer);
130 
131     }
132 
133  
134 
135     free(rbuffer);
136 
137     hdfsCloseFile(fs, readFile);
138 
139     /*
140 
141      * Disconnect to hdfs.
142 
143      */
144 
145     hdfsDisconnect(fs);
146 
147  
148 
149     return 0;
150 
151 }