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fix #16555, fixes #16405: len, high honors '\0' for cstring in vm (#16610)

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Timothee Cour 2021-01-11 01:16:20 -08:00 • committed by GitHub
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6 changed files with 74 additions and 15 deletions
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20
lib/system.nim
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@ -701,18 +701,24 @@ proc len*(x: string): int {.magic: "LengthStr", noSideEffect.}
## var str = "Hello world!"
## echo len(str) # => 12
proc len*(x: cstring): int {.magic: "LengthStr", noSideEffect.}
## Returns the length of a compatible string. This is sometimes
## an O(n) operation.
proc len*(x: cstring): int {.magic: "LengthStr", noSideEffect.} =
## Returns the length of a compatible string. This is an O(n) operation except
## in js at runtime.
##
## **Note:** On the JS backend this currently counts UTF-16 code points
## instead of bytes at runtime (not at compile time). For now, if you
## need the byte length of the UTF-8 encoding, convert to string with
## `$` first then call `len`.
##
## .. code-block:: Nim
## var str: cstring = "Hello world!"
## len(str) # => 12
runnableExamples:
doAssert len(cstring"abc") == 3
doAssert len(cstring r"ab\0c") == 5 # \0 is escaped
doAssert len(cstring"ab\0c") == 5 # ditto
var a: cstring = "ab\0c"
when defined(js): doAssert a.len == 4 # len ignores \0 for js
else: doAssert a.len == 2 # \0 is a null terminator
static:
var a2: cstring = "ab\0c"
doAssert a2.len == 2 # \0 is a null terminator, even in js vm
proc len*(x: (type array)|array): int {.magic: "LengthArray", noSideEffect.}
## Returns the length of an array or an array type.