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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.
type
NimStrPayloadBase = object
cap: int
NimStrPayload {.core.} = object
cap: int
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.cap and strlitFlag) == strlitFlag
template contentSize(cap): int = cap + 1 + sizeof(NimStrPayloadBase)
template frees(s) =
if not isLiteral(s):
when compileOption("threads"):
deallocShared(s.p)
else:
dealloc(s.p)
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.} =
let newLen = s.len + addlen
if isLiteral(s):
let oldP = s.p
# can't mutate a literal, so we need a fresh copy here:
when compileOption("threads"):
s.p = cast[ptr NimStrPayload](allocShared0(contentSize(newLen)))
else:
s.p = cast[ptr NimStrPayload](alloc0(contentSize(newLen)))
s.p.cap = newLen
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], min(s.len, newLen))
else:
let oldCap = s.p.cap and not strlitFlag
if newLen > oldCap:
let newCap = max(newLen, resize(oldCap))
when compileOption("threads"):
s.p = cast[ptr NimStrPayload](reallocShared0(s.p, contentSize(oldCap), contentSize(newCap)))
else:
s.p = cast[ptr NimStrPayload](realloc0(s.p, contentSize(oldCap), contentSize(newCap)))
s.p.cap = newCap
proc nimAddCharV1(s: var NimStringV2; c: char) {.compilerRtl, inline.} =
#if (s.p == nil) or (s.len+1 > s.p.cap and not strlitFlag):
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:
when compileOption("threads"):
var p = cast[ptr NimStrPayload](allocShared0(contentSize(len)))
else:
var p = cast[ptr NimStrPayload](alloc0(contentSize(len)))
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:
when compileOption("threads"):
var p = cast[ptr NimStrPayload](allocShared0(contentSize(space)))
else:
var p = cast[ptr NimStrPayload](alloc0(contentSize(space)))
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:
when compileOption("threads"):
var p = cast[ptr NimStrPayload](allocShared0(contentSize(len)))
else:
var p = cast[ptr NimStrPayload](alloc0(contentSize(len)))
p.cap = len
result = NimStringV2(len: len, p: p)
proc setLengthStrV2(s: var NimStringV2, newLen: int) {.compilerRtl.} =
if newLen == 0:
discard "do not free the buffer here, pattern 's.setLen 0' is common for avoiding allocations"
else:
if newLen > s.len or isLiteral(s):
prepareAdd(s, newLen - s.len)
s.p.data[newLen] = '\0'
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 and not strlitFlag) < b.len:
# 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)
when compileOption("threads"):
a.p = cast[ptr NimStrPayload](allocShared0(contentSize(b.len)))
else:
a.p = cast[ptr NimStrPayload](alloc0(contentSize(b.len)))
a.p.cap = b.len
a.len = b.len
copyMem(unsafeAddr a.p.data[0], unsafeAddr b.p.data[0], b.len+1)
proc nimPrepareStrMutationImpl(s: var NimStringV2) =
let oldP = s.p
# can't mutate a literal, so we need a fresh copy here:
when compileOption("threads"):
s.p = cast[ptr NimStrPayload](allocShared0(contentSize(s.len)))
else:
s.p = cast[ptr NimStrPayload](alloc0(contentSize(s.len)))
s.p.cap = s.len
copyMem(unsafeAddr s.p.data[0], unsafeAddr oldP.data[0], s.len+1)
proc nimPrepareStrMutationV2(s: var NimStringV2) {.compilerRtl, inline.} =
if s.p != nil and (s.p.cap and strlitFlag) == strlitFlag:
nimPrepareStrMutationImpl(s)
proc prepareMutation*(s: var string) {.inline.} =
# string literals are "copy on write", so you need to call
# `prepareMutation` before modifying the strings via `addr`.
{.cast(noSideEffect).}:
let s = unsafeAddr s
nimPrepareStrMutationV2(cast[ptr NimStringV2](s)[])
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