이 예제는 파일의 앞부분의 지정한 크기만큼을 삭제하고 그만큼 데이터를 앞으로 당겨주는 것입니다.
즉, LOG파일같은것을 다룰때 파일의 크기가 일정한 크기를 넘어섰을때 어떻게 빠르게 파일의 크기를 축소할수 있는지를 고민해보자는 취지에서 만들어 본것입니다.
reduce_file.tar.bz2즉, LOG파일같은것을 다룰때 파일의 크기가 일정한 크기를 넘어섰을때 어떻게 빠르게 파일의 크기를 축소할수 있는지를 고민해보자는 취지에서 만들어 본것입니다.
| 코드: |
| /* Copyright (C) Information Equipment co.,LTD All rights reserved. Code by JaeHyuk Cho <mailto:minzkn@infoeq.com> CVSTAG="$Header$" */ #if defined(WIN32) # include <io.h> # include <windows.h> #endif #include <sys/types.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <fcntl.h> #if !defined(O_BINARY) # define O_BINARY 0 #endif #if !defined(O_LARGEFILE) # define O_LARGEFILE 0 #endif #define def_max_block_size ((size_t)(4 << 10)) int main(int s_argc, char **s_argv) { const char *s_filename; size_t s_reduce_size, s_buffer_size; int s_handle; void *s_buffer; off_t s_roffset, s_woffset, s_filesize; ssize_t s_read_bytes, s_write_bytes; if(s_argc <= 2){ (void)fprintf(stdout, "Usage: %s <filepath> <reduce_size>\n", s_argv[0]); return(0); } s_filename = s_argv[1], s_reduce_size = (size_t)atoi(s_argv[2]); if(s_reduce_size <= ((size_t)0)){ (void)fprintf(stdout, "invalid reduce size !\n"); return(1); } s_buffer_size = (s_reduce_size > def_max_block_size) ? def_max_block_size : s_reduce_size; /* buffer_size limit check */ (void)fprintf(stdout, "debug: buffer_size=%lu\n", (unsigned long)s_buffer_size); s_handle = open(s_filename, O_RDWR | O_BINARY | O_LARGEFILE); if(s_handle == (-1)){ (void)fprintf(stdout, "can not open file ! (filename=\"%s\")\n", s_filename); return(1); } s_filesize = lseek(s_handle, (off_t)0, SEEK_END); if(s_filesize != ((off_t)(-1))) { s_buffer = malloc(s_buffer_size), s_roffset = (off_t)s_reduce_size, s_woffset = (off_t)0; if(s_buffer != ((void *)0)) { do { if(lseek(s_handle, s_roffset, SEEK_SET) == ((off_t)(-1)))break; s_read_bytes = read(s_handle, s_buffer, s_buffer_size); if(s_read_bytes <= ((ssize_t)0))break; s_roffset += (off_t)s_read_bytes; if(lseek(s_handle, s_woffset, SEEK_SET) == ((off_t)(-1)))break; s_write_bytes = write(s_handle, s_buffer, (size_t)s_read_bytes); if(s_write_bytes <= ((ssize_t)0))break; s_woffset += (off_t)s_write_bytes; }while(1); free(s_buffer); #if defined __USE_BSD || defined __USE_XOPEN_EXTENDED (void)fprintf(stdout, "truncate %llu -> %llu bytes\n", (unsigned long long)s_filesize, (unsigned long long)s_woffset); (void)ftruncate(s_handle, s_woffset); /* POSIX */ #elif defined(WIN32) (void)fprintf(stdout, "truncate %lu -> %lu bytes\n", (unsigned long)s_filesize, (unsigned long)s_woffset); (void)chsize(s_handle, s_woffset); #else # warning not supported (f)truncate | chsize #endif } else { (void)fprintf(stdout, "not enough memory\n"); return(1); } } else { (void)fprintf(stdout, "seek not supported\n"); return(1); } (void)close(s_handle); return(0); } /* vim: set expandtab: */ /* End of source */ |
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