add mmap_readat
parent
82b17dbfe3
commit
5c999f4c62
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.TH mmap_readat 3
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.SH NAME
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mmap_readat \- memory map a file for reading
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.SH SYNTAX
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.B #include <mmap.h>
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char* \fBmmap_readat\fP(const char* \fIfilename\fR,size_t* \fIfilesize\fR,int \fIdirfd\fR);
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.SH DESCRIPTION
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mmap_readat opens \fIfilename\fR for reading, maps the whole file into
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memory, closes the file, writes the length of the file to \fIfilesize\fR
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and returns a pointer to the mapped file.
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If \fIfilename\fR is a relative path and \fIdirfd\fR is not -1,
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\fIfilename\fR is interpreted relative to \fIdirfd\fR, which must be an
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open directory.
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The file is unmapped by the operating system if the process terminates.
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It can also be manually unmapped by calling \fBmunmap\fR from
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<sys/mman.h>.
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If the file could not be opened or mapped, (void*)0 is returned.
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.SH "SEE ALSO"
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mmap_unmap(3)
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#define _POSIX_C_SOURCE 200809
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#define _ATFILE_SOURCE
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#include <sys/types.h>
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#include <unistd.h>
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#ifndef __MINGW32__
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#include <sys/stat.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <sys/mman.h>
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#endif
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#include "open.h"
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#include "mmap.h"
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extern const char* mmap_readat(const char* filename,size_t * filesize,int dirfd) {
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#ifdef __MINGW32__
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return 0;
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#else
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int fd=openat(dirfd,filename,O_RDONLY);
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char *map;
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if (fd>=0) {
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register off_t o=lseek(fd,0,SEEK_END);
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if (sizeof(off_t)!=sizeof(size_t) && o > (off_t)(size_t)-1) { close(fd); return 0; }
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*filesize=(size_t)o;
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if (o>0) {
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map=mmap(0,*filesize,PROT_READ,MAP_SHARED,fd,0);
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if (map==(char*)-1)
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map=0;
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} else
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map="";
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close(fd);
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return map;
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}
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return 0;
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#endif
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}
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