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Diffstat (limited to 'lib/pure/reservedmem.nim')
| -rw-r--r-- | lib/pure/reservedmem.nim | 229 |
1 files changed, 229 insertions, 0 deletions
diff --git a/lib/pure/reservedmem.nim b/lib/pure/reservedmem.nim new file mode 100644 index 000000000..ffa0128dc --- /dev/null +++ b/lib/pure/reservedmem.nim @@ -0,0 +1,229 @@ +# +# +# Nim's Runtime Library +# (c) Copyright 2015 Nim Contributors +# +# See the file "copying.txt", included in this +# distribution, for details about the copyright. +# + +## :Authors: Zahary Karadjov +## +## This module provides utilities for reserving portions of the +## address space of a program without consuming physical memory. +## It can be used to implement a dynamically resizable buffer that +## is guaranteed to remain in the same memory location. The buffer +## will be able to grow up to the size of the initially reserved +## portion of the address space. +## +## Unstable API. + +from std/oserrors import raiseOSError, osLastError + +when defined(nimPreviewSlimSystem): + import std/assertions + +template distance*(lhs, rhs: pointer): int = + cast[int](rhs) - cast[int](lhs) + +template shift*(p: pointer, distance: int): pointer = + cast[pointer](cast[int](p) + distance) + +type + MemAccessFlags* = int + + ReservedMem* = object + memStart: pointer + usedMemEnd: pointer + committedMemEnd: pointer + memEnd: pointer + maxCommittedAndUnusedPages: int + accessFlags: MemAccessFlags + + ReservedMemSeq*[T] = object + mem: ReservedMem + +when defined(windows): + import std/winlean + import std/private/win_getsysteminfo + + proc getAllocationGranularity: uint = + var sysInfo: SystemInfo + getSystemInfo(addr sysInfo) + return uint(sysInfo.dwAllocationGranularity) + + let allocationGranularity = getAllocationGranularity().int + + const + memNoAccess = MemAccessFlags(PAGE_NOACCESS) + memExec* = MemAccessFlags(PAGE_EXECUTE) + memExecRead* = MemAccessFlags(PAGE_EXECUTE_READ) + memExecReadWrite* = MemAccessFlags(PAGE_EXECUTE_READWRITE) + memRead* = MemAccessFlags(PAGE_READONLY) + memReadWrite* = MemAccessFlags(PAGE_READWRITE) + + template check(expr) = + let r = expr + if r == cast[typeof(r)](0): + raiseOSError(osLastError()) + +else: + import std/posix + + let allocationGranularity = sysconf(SC_PAGESIZE) + + let + memNoAccess = MemAccessFlags(PROT_NONE) + memExec* = MemAccessFlags(PROT_EXEC) + memExecRead* = MemAccessFlags(PROT_EXEC or PROT_READ) + memExecReadWrite* = MemAccessFlags(PROT_EXEC or PROT_READ or PROT_WRITE) + memRead* = MemAccessFlags(PROT_READ) + memReadWrite* = MemAccessFlags(PROT_READ or PROT_WRITE) + + template check(expr) = + if not expr: + raiseOSError(osLastError()) + +func nextAlignedOffset(n, alignment: int): int = + result = n + let m = n mod alignment + if m != 0: result += alignment - m + + +when defined(windows): + const + MEM_DECOMMIT = 0x4000 + MEM_RESERVE = 0x2000 + MEM_COMMIT = 0x1000 + proc virtualFree(lpAddress: pointer, dwSize: int, + dwFreeType: int32): cint {.header: "<windows.h>", stdcall, + importc: "VirtualFree".} + proc virtualAlloc(lpAddress: pointer, dwSize: int, flAllocationType, + flProtect: int32): pointer {. + header: "<windows.h>", stdcall, importc: "VirtualAlloc".} + +proc init*(T: type ReservedMem, + maxLen: Natural, + initLen: Natural = 0, + initCommitLen = initLen, + memStart = pointer(nil), + accessFlags = memReadWrite, + maxCommittedAndUnusedPages = 3): ReservedMem = + + assert initLen <= initCommitLen + let commitSize = nextAlignedOffset(initCommitLen, allocationGranularity) + + when defined(windows): + result.memStart = virtualAlloc(memStart, maxLen, MEM_RESERVE, + accessFlags.cint) + check result.memStart + if commitSize > 0: + check virtualAlloc(result.memStart, commitSize, MEM_COMMIT, + accessFlags.cint) + else: + var allocFlags = MAP_PRIVATE or MAP_ANONYMOUS # or MAP_NORESERVE + # if memStart != nil: + # allocFlags = allocFlags or MAP_FIXED_NOREPLACE + result.memStart = mmap(memStart, maxLen, PROT_NONE, allocFlags, -1, 0) + check result.memStart != MAP_FAILED + if commitSize > 0: + check mprotect(result.memStart, commitSize, cint(accessFlags)) == 0 + + result.usedMemEnd = result.memStart.shift(initLen) + result.committedMemEnd = result.memStart.shift(commitSize) + result.memEnd = result.memStart.shift(maxLen) + result.accessFlags = accessFlags + result.maxCommittedAndUnusedPages = maxCommittedAndUnusedPages + +func len*(m: ReservedMem): int = + distance(m.memStart, m.usedMemEnd) + +func commitedLen*(m: ReservedMem): int = + distance(m.memStart, m.committedMemEnd) + +func maxLen*(m: ReservedMem): int = + distance(m.memStart, m.memEnd) + +proc setLen*(m: var ReservedMem, newLen: int) = + let len = m.len + m.usedMemEnd = m.memStart.shift(newLen) + if newLen > len: + let d = distance(m.committedMemEnd, m.usedMemEnd) + if d > 0: + let commitExtensionSize = nextAlignedOffset(d, allocationGranularity) + when defined(windows): + check virtualAlloc(m.committedMemEnd, commitExtensionSize, + MEM_COMMIT, m.accessFlags.cint) + else: + check mprotect(m.committedMemEnd, commitExtensionSize, + m.accessFlags.cint) == 0 + else: + let d = distance(m.usedMemEnd, m.committedMemEnd) - + m.maxCommittedAndUnusedPages * allocationGranularity + if d > 0: + let commitSizeShrinkage = nextAlignedOffset(d, allocationGranularity) + let newCommitEnd = m.committedMemEnd.shift(-commitSizeShrinkage) + + when defined(windows): + check virtualFree(newCommitEnd, commitSizeShrinkage, MEM_DECOMMIT) + else: + check posix_madvise(newCommitEnd, commitSizeShrinkage, + POSIX_MADV_DONTNEED) == 0 + + m.committedMemEnd = newCommitEnd + +proc init*(SeqType: type ReservedMemSeq, + maxLen: Natural, + initLen: Natural = 0, + initCommitLen: Natural = 0, + memStart = pointer(nil), + accessFlags = memReadWrite, + maxCommittedAndUnusedPages = 3): SeqType = + + let elemSize = sizeof(SeqType.T) + result.mem = ReservedMem.init(maxLen * elemSize, + initLen * elemSize, + initCommitLen * elemSize, + memStart, accessFlags, + maxCommittedAndUnusedPages) + +func `[]`*[T](s: ReservedMemSeq[T], pos: Natural): lent T = + let elemAddr = s.mem.memStart.shift(pos * sizeof(T)) + rangeCheck elemAddr < s.mem.usedMemEnd + result = (cast[ptr T](elemAddr))[] + +func `[]`*[T](s: var ReservedMemSeq[T], pos: Natural): var T = + let elemAddr = s.mem.memStart.shift(pos * sizeof(T)) + rangeCheck elemAddr < s.mem.usedMemEnd + result = (cast[ptr T](elemAddr))[] + +func `[]`*[T](s: ReservedMemSeq[T], rpos: BackwardsIndex): lent T = + return s[int(s.len) - int(rpos)] + +func `[]`*[T](s: var ReservedMemSeq[T], rpos: BackwardsIndex): var T = + return s[int(s.len) - int(rpos)] + +func len*[T](s: ReservedMemSeq[T]): int = + s.mem.len div sizeof(T) + +proc setLen*[T](s: var ReservedMemSeq[T], newLen: int) = + # TODO call destructors + s.mem.setLen(newLen * sizeof(T)) + +proc add*[T](s: var ReservedMemSeq[T], val: T) = + let len = s.len + s.setLen(len + 1) + s[len] = val + +proc pop*[T](s: var ReservedMemSeq[T]): T = + assert s.usedMemEnd != s.memStart + let lastIdx = s.len - 1 + result = s[lastIdx] + s.setLen(lastIdx) + +func commitedLen*[T](s: ReservedMemSeq[T]): int = + s.mem.commitedLen div sizeof(T) + +func maxLen*[T](s: ReservedMemSeq[T]): int = + s.mem.maxLen div sizeof(T) + |