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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)
template allocPayload(newLen: int): ptr NimStrPayload =
when compileOption("threads"):
cast[ptr NimStrPayload](allocShared(contentSize(newLen)))
else:
cast[ptr NimStrPayload](alloc(contentSize(newLen)))
template allocPayload0(newLen: int): ptr NimStrPayload =
when compileOption("threads"):
cast[ptr NimStrPayload](allocShared0(contentSize(newLen)))
else:
cast[ptr NimStrPayload](alloc0(contentSize(newLen)))
template reallocPayload(p: pointer, newLen: int): ptr NimStrPayload =
when compileOption("threads"):
cast[ptr NimStrPayload](reallocShared(p, contentSize(newLen)))
else:
cast[ptr NimStrPayload](realloc(p, contentSize(newLen)))
template reallocPayload0(p: pointer; oldLen, newLen: int): ptr NimStrPayload =
when compileOption("threads"):
cast[ptr NimStrPayload](reallocShared0(p, contentSize(oldLen), contentSize(newLen)))
else:
cast[ptr NimStrPayload](realloc0(p, contentSize(oldLen), contentSize(newLen)))
proc resize(old: int): int {.inline.} =
if old <= 0: result = 4
elif old <= high(int16): 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:
s.p = allocPayload(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))
elif oldP == nil:
# In the case of `newString(0) & ""`, since `src.len == 0`, `appendString`
# will not set the `\0` terminator, so we set it here.
s.p.data[0] = '\0'
else:
let oldCap = s.p.cap and not strlitFlag
if newLen > oldCap:
let newCap = max(newLen, resize(oldCap))
s.p = reallocPayload(s.p, newCap)
s.p.cap = newCap
if newLen < newCap:
zeroMem(cast[pointer](addr s.p.data[newLen+1]), newCap - newLen)
proc nimAddCharV1(s: var NimStringV2; c: char) {.compilerRtl, inl.} =
#if (s.p == nil) or (s.len+1 > s.p.cap and not strlitFlag):
prepareAdd(s, 1)
s.p.data[s.len] = c
inc s.len
s.p.data[s.len] = '\0'
proc toNimStr(str: cstring, len: int): NimStringV2 {.compilerproc.} =
if len <= 0:
result = NimStringV2(len: 0, p: nil)
else:
var p = allocPayload(len)
p.cap = len
copyMem(unsafeAddr p.data[0], str, len+1)
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 = cast[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
inc dest.len
dest.p.data[dest.len] = '\0'
proc rawNewString(space: int): NimStringV2 {.compilerproc.} =
# this is also 'system.newStringOfCap'.
if space <= 0:
result = NimStringV2(len: 0, p: nil)
else:
var p = allocPayload(space)
p.cap = space
p.data[0] = '\0'
result = NimStringV2(len: 0, p: p)
proc mnewString(len: int): NimStringV2 {.compilerproc.} =
if len <= 0:
result = NimStringV2(len: 0, p: nil)
else:
var p = allocPayload0(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 isLiteral(s):
let oldP = s.p
s.p = allocPayload(newLen)
s.p.cap = newLen
if s.len > 0:
copyMem(unsafeAddr s.p.data[0], unsafeAddr oldP.data[0], min(s.len, newLen))
if newLen > s.len:
zeroMem(cast[pointer](addr s.p.data[s.len]), newLen - s.len + 1)
else:
s.p.data[newLen] = '\0'
else:
zeroMem(cast[pointer](addr s.p.data[0]), newLen + 1)
elif newLen > s.len:
let oldCap = s.p.cap and not strlitFlag
if newLen > oldCap:
let newCap = max(newLen, resize(oldCap))
s.p = reallocPayload0(s.p, oldCap, newCap)
s.p.cap = newCap
s.p.data[newLen] = '\0'
s.len = newLen
proc nimAsgnStrV2(a: var NimStringV2, b: NimStringV2) {.compilerRtl.} =
if a.p == b.p and a.len == b.len: 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)
a.p = allocPayload(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:
s.p = allocPayload(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, inl.} =
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)[])
proc nimAddStrV1(s: var NimStringV2; src: NimStringV2) {.compilerRtl, inl.} =
#if (s.p == nil) or (s.len+1 > s.p.cap and not strlitFlag):
prepareAdd(s, src.len)
appendString s, src
proc nimDestroyStrV1(s: NimStringV2) {.compilerRtl, inl.} =
frees(s)
proc nimStrAtLe(s: string; idx: int; ch: char): bool {.compilerRtl, inl.} =
result = idx < s.len and s[idx] <= ch
func capacity*(self: string): int {.inline.} =
## Returns the current capacity of the string.
# See https://github.com/nim-lang/RFCs/issues/460
runnableExamples:
var str = newStringOfCap(cap = 42)
str.add "Nim"
assert str.capacity == 42
let str = cast[ptr NimStringV2](unsafeAddr self)
result = if str.p != nil: str.p.cap and not strlitFlag else: 0
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