Join MDN and developers like you at Mozilla's View Source conference, 12-14 September in Berlin, Germany. Learn more at


Maps a section of a file to memory.


#include <prio.h> 

void* PR_MemMap(
  PRFileMap *fmap,
  PRInt64 offset,
  PRUint32 len);


The function has the following parameters:

A pointer to the file-mapping object representing the file to be memory-mapped.
The starting offset of the section of file to be mapped. The offset must be aligned to whole pages.
Length of the section of the file to be mapped.


The starting address of the memory region to which the section of file is mapped. Returns NULL on error.


PR_MemMap maps a section of the file represented by the file mapping fmap to memory. The section of the file starts at offset and has the length len.

When the file-mapping memory region is no longer needed, it should be unmapped with a call to PR_MemUnmap.

Document Tags and Contributors

 Contributors to this page: teoli, Wtchang, Rappo
 Last updated by: teoli,