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[Mmap] Turn PAGESIZE into a function #59712

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[Mmap] Turn PAGESIZE into a function #59712

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b8477d6
[Mmap] Turn `PAGESIZE` into a function
giordano Sep 30, 2025
28aa688
[Mmap] Seek file back to beginning before running next test in mmap
green-br Sep 30, 2025
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10 changes: 5 additions & 5 deletions stdlib/Mmap/src/Mmap.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ import Base: OS_HANDLE, INVALID_OS_HANDLE

export mmap

const PAGESIZE = Int(Sys.isunix() ? ccall(:jl_getpagesize, Clong, ()) : ccall(:jl_getallocationgranularity, Clong, ()))
pagesize() = Int(Sys.isunix() ? ccall(:jl_getpagesize, Clong, ()) : ccall(:jl_getallocationgranularity, Clong, ()))

# for mmaps not backed by files
mutable struct Anonymous <: IO
Expand Down Expand Up @@ -200,12 +200,12 @@ function mmap(io::IO,
end
len >= 0 || throw(ArgumentError("requested size must be ≥ 0, got $len"))
len == 0 && return Array{T}(undef, ntuple(x->0,Val(N)))
len < typemax(Int) - PAGESIZE || throw(ArgumentError("requested size must be < $(typemax(Int)-PAGESIZE), got $len"))
len < typemax(Int) - pagesize() || throw(ArgumentError("requested size must be < $(typemax(Int)-pagesize()), got $len"))

offset >= 0 || throw(ArgumentError("requested offset must be ≥ 0, got $offset"))

# shift `offset` to start of page boundary
offset_page::Int64 = div(offset, PAGESIZE) * PAGESIZE
offset_page::Int64 = div(offset, pagesize()) * pagesize()
# add (offset - offset_page) to `len` to get total length of memory-mapped region
mmaplen = (offset - offset_page) + len

Expand Down Expand Up @@ -365,7 +365,7 @@ Forces synchronization between the in-memory version of a memory-mapped `Array`
"""
function sync!(m::Array, flags::Integer=MS_SYNC)
ptr = pointer(m)
offset = rem(UInt(ptr), PAGESIZE)
offset = rem(UInt(ptr), pagesize())
ptr = ptr - offset
mmaplen = sizeof(m) + offset
GC.@preserve m @static if Sys.isunix()
Expand Down Expand Up @@ -428,7 +428,7 @@ Advises the kernel on the intended usage of the memory-mapped `array`, with the
"""
function madvise!(m::Array, flag::Integer=MADV_NORMAL)
ptr = pointer(m)
offset = rem(UInt(ptr), PAGESIZE)
offset = rem(UInt(ptr), pagesize())
ptr = ptr - offset
mmaplen = sizeof(m) + offset
GC.@preserve m begin
Expand Down
1 change: 1 addition & 0 deletions stdlib/Mmap/test/runtests.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -268,6 +268,7 @@ A2 = mmap(s, Matrix{Int}, (m,n))
seek(s, 0)
A3 = mmap(s, Matrix{Int}, (m,n), convert(Int64, 2*sizeof(Int)))
@test A == A3
seek(s, 0)
A4 = mmap(s, Matrix{Int}, (m,150), convert(Int64, (2+150*m)*sizeof(Int)))
@test A[:, 151:end] == A4
close(s)
Expand Down