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#
#
# Nim's Runtime Library
# (c) Copyright 2017 Nim contributors
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## Default new string implementation used by Nim's core.
import allocators
type
NimStrPayload {.core.} = object
cap: int
allocator: Allocator
data: UncheckedArray[char]
NimStringV2 {.core.} = object
len: int
p: ptr NimStrPayload ## can be nil if len == 0.
const nimStrVersion {.core.} = 2
template isLiteral(s): bool = s.p == nil or s.p.allocator == nil
template contentSize(cap): int = cap + 1 + sizeof(int) + sizeof(Allocator)
template frees(s) =
if not isLiteral(s):
s.p.allocator.dealloc(s.p.allocator, s.p, contentSize(s.p.cap))
proc resize(old: int): int {.inline.} =
if old <= 0: result = 4
elif old < 65536: result = old * 2
else: result = old * 3 div 2 # for large arrays * 3/2 is better
proc prepareAdd(s: var NimStringV2; addlen: int) {.compilerRtl.} =
if isLiteral(s) and addlen > 0:
let oldP = s.p
# can't mutate a literal, so we need a fresh copy here:
let allocator = getLocalAllocator()
s.p = cast[ptr NimStrPayload](allocator.alloc(allocator, contentSize(s.len + addlen)))
s.p.allocator = allocator
s.p.cap = s.len + addlen
if s.len > 0:
# we are about to append, so there is no need to copy the \0 terminator:
copyMem(unsafeAddr s.p.data[0], unsafeAddr oldP.data[0], s.len)
elif s.len + addlen > s.p.cap:
let cap = max(s.len + addlen, resize(s.p.cap))
s.p = cast[ptr NimStrPayload](s.p.allocator.realloc(s.p.allocator, s.p,
oldSize = contentSize(s.p.cap),
newSize = contentSize(cap)))
s.p.cap = cap
proc nimAddCharV1(s: var NimStringV2; c: char) {.compilerRtl.} =
prepareAdd(s, 1)
s.p.data[s.len] = c
s.p.data[s.len+1] = '\0'
inc s.len
proc toNimStr(str: cstring, len: int): NimStringV2 {.compilerproc.} =
if len <= 0:
result = NimStringV2(len: 0, p: nil)
else:
let allocator = getLocalAllocator()
var p = cast[ptr NimStrPayload](allocator.alloc(allocator, contentSize(len)))
p.allocator = allocator
p.cap = len
if len > 0:
# we are about to append, so there is no need to copy the \0 terminator:
copyMem(unsafeAddr p.data[0], str, len)
result = NimStringV2(len: len, p: p)
proc cstrToNimstr(str: cstring): NimStringV2 {.compilerRtl.} =
if str == nil: toNimStr(str, 0)
else: toNimStr(str, str.len)
proc nimToCStringConv(s: NimStringV2): cstring {.compilerproc, nonReloadable, inline.} =
if s.len == 0: result = cstring""
else: result = cstring(unsafeAddr s.p.data)
proc appendString(dest: var NimStringV2; src: NimStringV2) {.compilerproc, inline.} =
if src.len > 0:
# also copy the \0 terminator:
copyMem(unsafeAddr dest.p.data[dest.len], unsafeAddr src.p.data[0], src.len+1)
inc dest.len, src.len
proc appendChar(dest: var NimStringV2; c: char) {.compilerproc, inline.} =
dest.p.data[dest.len] = c
dest.p.data[dest.len+1] = '\0'
inc dest.len
proc rawNewString(space: int): NimStringV2 {.compilerproc.} =
# this is also 'system.newStringOfCap'.
if space <= 0:
result = NimStringV2(len: 0, p: nil)
else:
let allocator = getLocalAllocator()
var p = cast[ptr NimStrPayload](allocator.alloc(allocator, contentSize(space)))
p.allocator = allocator
p.cap = space
result = NimStringV2(len: 0, p: p)
proc mnewString(len: int): NimStringV2 {.compilerproc.} =
if len <= 0:
result = NimStringV2(len: 0, p: nil)
else:
let allocator = getLocalAllocator()
var p = cast[ptr NimStrPayload](allocator.alloc(allocator, contentSize(len)))
p.allocator = allocator
p.cap = len
result = NimStringV2(len: len, p: p)
proc setLengthStrV2(s: var NimStringV2, newLen: int) {.compilerRtl.} =
if newLen == 0:
frees(s)
s.p = nil
elif newLen > s.len or isLiteral(s):
prepareAdd(s, newLen - s.len)
s.len = newLen
proc nimAsgnStrV2(a: var NimStringV2, b: NimStringV2) {.compilerRtl.} =
if a.p == b.p: return
if isLiteral(b):
# we can shallow copy literals:
frees(a)
a.len = b.len
a.p = b.p
else:
if isLiteral(a) or a.p.cap < b.len:
let allocator = if a.p != nil and a.p.allocator != nil: a.p.allocator else: getLocalAllocator()
# we have to allocate the 'cap' here, consider
# 'let y = newStringOfCap(); var x = y'
# on the other hand... These get turned into moves now.
frees(a)
a.p = cast[ptr NimStrPayload](allocator.alloc(allocator, contentSize(b.len)))
a.p.allocator = allocator
a.p.cap = b.len
a.len = b.len
copyMem(unsafeAddr a.p.data[0], unsafeAddr b.p.data[0], b.len+1)
proc nimPrepareStrMutationV2(s: var NimStringV2) {.compilerRtl.} =
if s.p != nil and s.p.allocator == nil:
let oldP = s.p
# can't mutate a literal, so we need a fresh copy here:
let allocator = getLocalAllocator()
s.p = cast[ptr NimStrPayload](allocator.alloc(allocator, contentSize(s.len)))
s.p.allocator = allocator
s.p.cap = s.len
copyMem(unsafeAddr s.p.data[0], unsafeAddr oldP.data[0], s.len+1)
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