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| author | Iain Buclaw <ibuclaw@gdcproject.org> | 2024-01-18 02:39:20 +0100 |
|---|---|---|
| committer | Iain Buclaw <ibuclaw@gdcproject.org> | 2024-02-03 00:49:46 +0100 |
| commit | f204359931866b917856fc959c70dbf55f28c14d (patch) | |
| tree | ba1c671045e384fa49a6381f79abf7c1b84a55ea /libphobos/src/std/mmfile.d | |
| parent | 5470a9b176c2b3030ff3891c7e9403db2b0685b8 (diff) | |
| download | gcc-f204359931866b917856fc959c70dbf55f28c14d.zip gcc-f204359931866b917856fc959c70dbf55f28c14d.tar.gz gcc-f204359931866b917856fc959c70dbf55f28c14d.tar.bz2 | |
d: Merge dmd, druntime bce5c1f7b5, phobos e4d0dd513.
D front-end changes:
- Import latest changes from dmd v2.107.0-beta.1.
- Keywords like `__FILE__' are now always evaluated at the
callsite.
D runtime changes:
- Import latest changes from druntime v2.107.0-beta.1.
- Added `nameSig' field to TypeInfo_Class in object.d.
Phobos changes:
- Import latest changes from phobos v2.107.0-beta.1.
gcc/d/ChangeLog:
* dmd/MERGE: Merge upstream dmd bce5c1f7b5.
* d-attribs.cc (build_attributes): Update for new front-end interface.
* d-lang.cc (d_parse_file): Likewise.
* decl.cc (DeclVisitor::visit (VarDeclaration *)): Likewise.
* expr.cc (build_lambda_tree): New function.
(ExprVisitor::visit (FuncExp *)): Use build_lambda_tree.
(ExprVisitor::visit (SymOffExp *)): Likewise.
(ExprVisitor::visit (VarExp *)): Likewise.
* typeinfo.cc (create_tinfo_types): Add two ulong fields to internal
TypeInfo representation.
(TypeInfoVisitor::visit (TypeInfoClassDeclaration *)): Emit stub data
for TypeInfo_Class.nameSig.
(TypeInfoVisitor::visit (TypeInfoStructDeclaration *)): Update for new
front-end interface.
libphobos/ChangeLog:
* libdruntime/MERGE: Merge upstream druntime bce5c1f7b5.
* src/MERGE: Merge upstream phobos e4d0dd513.
Diffstat (limited to 'libphobos/src/std/mmfile.d')
| -rw-r--r-- | libphobos/src/std/mmfile.d | 68 |
1 files changed, 52 insertions, 16 deletions
diff --git a/libphobos/src/std/mmfile.d b/libphobos/src/std/mmfile.d index f8f8a90..b2cab31 100644 --- a/libphobos/src/std/mmfile.d +++ b/libphobos/src/std/mmfile.d @@ -2,10 +2,22 @@ /** * Read and write memory mapped files. + * + * Memory mapped files are a mechanism in operating systems that allows + * file access through virtual memory. After opening a file with `MmFile`, + * the contents can be read from or written to with standard slice / pointer operations. + * Changes to the memory are automatically reflected in the underlying file. + * + * Memory mapping can increase I/O performance of large files, compared to buffered + * read / write operations from `std.file` and `std.stdio`. However, I/O errors are + * not handled as safely: when for example the disk that the file is on gets removed, + * reading from it may result in a segfault. + * * Copyright: Copyright The D Language Foundation 2004 - 2009. * License: $(HTTP www.boost.org/LICENSE_1_0.txt, Boost License 1.0). * Authors: $(HTTP digitalmars.com, Walter Bright), * Matthew Wilson + * References: $(LINK https://en.wikipedia.org/wiki/Memory-mapped_file) * Source: $(PHOBOSSRC std/mmfile.d) * * $(SCRIPT inhibitQuickIndex = 1;) @@ -612,23 +624,47 @@ private: { static assert(0); } +} + +/// Read an existing file +@system unittest +{ + import std.file; + std.file.write(deleteme, "hello"); // deleteme is a temporary filename + scope(exit) remove(deleteme); + + // Use a scope class so the file will be closed at the end of this function + scope mmfile = new MmFile(deleteme); + + assert(mmfile.length == "hello".length); + + // Access file contents with the slice operator + // This is typed as `void[]`, so cast to `char[]` or `ubyte[]` to use it + const data = cast(const(char)[]) mmfile[]; + + // At this point, the file content may not have been read yet. + // In that case, the following memory access will intentionally + // trigger a page fault, causing the kernel to load the file contents + assert(data[0 .. 5] == "hello"); +} + +/// Write a new file +@system unittest +{ + import std.file; + scope(exit) remove(deleteme); + + scope mmfile = new MmFile(deleteme, MmFile.Mode.readWriteNew, 5, null); + assert(mmfile.length == 5); + + auto data = cast(ubyte[]) mmfile[]; + + // This write to memory will be reflected in the file contents + data[] = '\n'; + + mmfile.flush(); - // Report error, where errno gives the error number - // void errNo() - // { - // version (Windows) - // { - // throw new FileException(filename, GetLastError()); - // } - // else version (linux) - // { - // throw new FileException(filename, errno); - // } - // else - // { - // static assert(0); - // } - // } + assert(std.file.read(deleteme) == "\n\n\n\n\n"); } @system unittest |