mirror of https://github.com/status-im/nimPNG.git
andri lim
GitHub
commit
ed12086325
|
|
@ -0,0 +1,61 @@
|
|||
## Legacy API
|
||||
|
||||
```Nim
|
||||
proc encodePNG*(input: string, colorType: PNGColorType, bitDepth, w, h: int, settings = PNGEncoder(nil)): PNG
|
||||
proc encodePNG32*(input: string, w, h: int): PNG
|
||||
proc encodePNG24*(input: string, w, h: int): PNG
|
||||
|
||||
when not defined(js):
|
||||
proc savePNG*(fileName, input: string, colorType: PNGColorType, bitDepth, w, h: int): bool
|
||||
proc savePNG32*(fileName, input: string, w, h: int): bool
|
||||
proc savePNG24*(fileName, input: string, w, h: int): bool
|
||||
|
||||
proc prepareAPNG*(colorType: PNGColorType, bitDepth, numPlays: int, settings = PNGEncoder(nil)): PNG
|
||||
proc prepareAPNG24*(numPlays = 0): PNG
|
||||
proc prepareAPNG32*(numPlays = 0): PNG
|
||||
proc addDefaultImage*(png: PNG, input: string, width, height: int, ctl = APNGFrameControl(nil)): bool
|
||||
proc addFrame*(png: PNG, frame: string, ctl: APNGFrameControl): bool
|
||||
proc encodeAPNG*(png: PNG): string
|
||||
|
||||
when not defined(js):
|
||||
proc saveAPNG*(png: PNG, fileName: string): bool
|
||||
|
||||
proc decodePNG*(s: Stream, colorType: PNGColorType, bitDepth: int, settings = PNGDecoder(nil)): PNGResult
|
||||
proc decodePNG*(s: Stream, settings = PNGDecoder(nil)): PNG
|
||||
|
||||
when not defined(js):
|
||||
proc loadPNG*(fileName: string, colorType: PNGColorType, bitDepth: int, settings: PNGDecoder = nil): PNGResult
|
||||
proc loadPNG32*(fileName: string, settings = PNGDecoder(nil)): PNGResult
|
||||
proc loadPNG24*(fileName: string, settings = PNGDecoder(nil)): PNGResult
|
||||
|
||||
proc decodePNG32*(input: string, settings = PNGDecoder(nil)): PNGResult
|
||||
proc decodePNG24*(input: string, settings = PNGDecoder(nil)): PNGResult
|
||||
```
|
||||
|
||||
|
||||
## New API
|
||||
|
||||
|
||||
```Nim
|
||||
proc decodePNG*(T: type, s: Stream, colorType: PNGColorType, bitDepth: int, settings = PNGDecoder(nil)): PNGResult[T]
|
||||
proc decodePNG*(T: type, s: Stream, settings = PNGDecoder(nil)): PNG
|
||||
|
||||
type
|
||||
PNGRes*[T] = Result[PNGResult[T], string]
|
||||
|
||||
when not defined(js):
|
||||
proc loadPNG*(T: type, fileName: string, colorType: PNGColorType, bitDepth: int, settings: PNGDecoder = nil): PNGRes[T]
|
||||
proc loadPNG32*(T: type, fileName: string, settings = PNGDecoder(nil)): PNGRes[T]
|
||||
proc loadPNG24*(T: type, fileName: string, settings = PNGDecoder(nil)): PNGRes[T]
|
||||
|
||||
proc decodePNG32*(T: type, input: T, settings = PNGDecoder(nil)): PNGRes[T]
|
||||
proc decodePNG24*(T: type, input: T, settings = PNGDecoder(nil)): PNGRes[T]
|
||||
```
|
||||
|
||||
## How to use PNGRes?
|
||||
|
||||
```Nim
|
||||
let res = loadPNG32(seq[uint8], fileName, settings)
|
||||
if res.isOk: result = res.get() # get PNGResult[seq[uint8]]
|
||||
else: debugEcho res.error() # get error string
|
||||
```
|
||||
506
nimPNG.nim
506
nimPNG.nim
File diff suppressed because it is too large
Load Diff
|
|
@ -1,5 +1,5 @@
|
|||
# Package
|
||||
version = "0.2.7"
|
||||
version = "0.3.0"
|
||||
author = "Andri Lim"
|
||||
description = "PNG encoder and decoder"
|
||||
license = "MIT"
|
||||
|
|
|
|||
|
|
@ -0,0 +1,642 @@
|
|||
# nim-result is also available stand-alone from https://github.com/arnetheduck/nim-result/
|
||||
|
||||
# Copyright (c) 2019 Jacek Sieka
|
||||
# Licensed and distributed under either of
|
||||
# * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT).
|
||||
# * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
|
||||
# at your option. This file may not be copied, modified, or distributed except according to those terms.
|
||||
|
||||
type
|
||||
ResultError*[E] = object of ValueError
|
||||
## Error raised when using `tryGet` value of result when error is set
|
||||
## See also Exception bridge mode
|
||||
error*: E
|
||||
|
||||
ResultDefect* = object of Defect
|
||||
## Defect raised when accessing value when error is set and vice versa
|
||||
## See also Exception bridge mode
|
||||
|
||||
Result*[T, E] = object
|
||||
## Result type that can hold either a value or an error, but not both
|
||||
##
|
||||
## # Example
|
||||
##
|
||||
## ```
|
||||
## # It's convenient to create an alias - most likely, you'll do just fine
|
||||
## # with strings or cstrings as error
|
||||
##
|
||||
## type R = Result[int, string]
|
||||
##
|
||||
## # Once you have a type, use `ok` and `err`:
|
||||
##
|
||||
## func works(): R =
|
||||
## # ok says it went... ok!
|
||||
## R.ok 42
|
||||
## func fails(): R =
|
||||
## # or type it like this, to not repeat the type!
|
||||
## result.err "bad luck"
|
||||
##
|
||||
## if (let w = works(); w.isOk):
|
||||
## echo w[], " or use value: ", w.value
|
||||
##
|
||||
## # In case you think your callers want to differentiate between errors:
|
||||
## type
|
||||
## Error = enum
|
||||
## a, b, c
|
||||
## type RE[T] = Result[T, Error]
|
||||
##
|
||||
## # In the expriments corner, you'll find the following syntax for passing
|
||||
## # errors up the stack:
|
||||
## func f(): R =
|
||||
## let x = ?works() - ?fails()
|
||||
## assert false, "will never reach"
|
||||
##
|
||||
## # If you provide this exception converter, this exception will be raised
|
||||
## # on dereference
|
||||
## func toException(v: Error): ref CatchableError = (ref CatchableError)(msg: $v)
|
||||
## try:
|
||||
## RE[int].err(a)[]
|
||||
## except CatchableError:
|
||||
## echo "in here!"
|
||||
##
|
||||
## ```
|
||||
##
|
||||
## See the tests for more practical examples, specially when working with
|
||||
## back and forth with the exception world!
|
||||
##
|
||||
## # Potential benefits:
|
||||
##
|
||||
## * Handling errors becomes explicit and mandatory at the call site -
|
||||
## goodbye "out of sight, out of mind"
|
||||
## * Errors are a visible part of the API - when they change, so must the
|
||||
## calling code and compiler will point this out - nice!
|
||||
## * Errors are a visible part of the API - your fellow programmer is
|
||||
## reminded that things actually can go wrong
|
||||
## * Jives well with Nim `discard`
|
||||
## * Jives well with the new Defect exception hierarchy, where defects
|
||||
## are raised for unrecoverable errors and the rest of the API uses
|
||||
## results
|
||||
## * Error and value return have similar performance characteristics
|
||||
## * Caller can choose to turn them into exceptions at low cost - flexible
|
||||
## for libraries!
|
||||
## * Mostly relies on simple Nim features - though this library is no
|
||||
## exception in that compiler bugs were discovered writing it :)
|
||||
##
|
||||
## # Potential costs:
|
||||
##
|
||||
## * Handling errors becomes explicit and mandatory - if you'd rather ignore
|
||||
## them or just pass them to some catch-all, this is noise
|
||||
## * When composing operations, value must be lifted before processing,
|
||||
## adding potential verbosity / noise (fancy macro, anyone?)
|
||||
## * There's no call stack captured by default (see also `catch` and
|
||||
## `capture`)
|
||||
## * The extra branching may be more expensive for the non-error path
|
||||
## (though this can be minimized with PGO)
|
||||
##
|
||||
## The API visibility issue of exceptions can also be solved with
|
||||
## `{.raises.}` annotations - as of now, the compiler doesn't remind
|
||||
## you to do so, even though it knows what the right annotation should be.
|
||||
## `{.raises.}` does not participate in generic typing, making it just as
|
||||
## verbose but less flexible in some ways, if you want to type it out.
|
||||
##
|
||||
## Many system languages make a distinction between errors you want to
|
||||
## handle and those that are simply bugs or unrealistic to deal with..
|
||||
## handling the latter will often involve aborting or crashing the funcess -
|
||||
## reliable systems like Erlang will try to relaunch it.
|
||||
##
|
||||
## On the flip side we have dynamic languages like python where there's
|
||||
## nothing exceptional about exceptions (hello StopIterator). Python is
|
||||
## rarely used to build reliable systems - its strengths lie elsewhere.
|
||||
##
|
||||
## # Exception bridge mode
|
||||
##
|
||||
## When the error of a `Result` is an `Exception`, or a `toException` helper
|
||||
## is present for your error type, the "Exception bridge mode" is
|
||||
## enabled and instead of raising `ResultError`, `tryGet` will raise the
|
||||
## given `Exception` on access. `[]` and `get` will continue to raise a
|
||||
## `Defect`.
|
||||
##
|
||||
## This is an experimental feature that may be removed.
|
||||
##
|
||||
## # Other languages
|
||||
##
|
||||
## Result-style error handling seems pretty popular lately, specially with
|
||||
## statically typed languages:
|
||||
## Haskell: https://hackage.haskell.org/package/base-4.11.1.0/docs/Data-Either.html
|
||||
## Rust: https://doc.rust-lang.org/std/result/enum.Result.html
|
||||
## Modern C++: https://github.com/viboes/std-make/tree/master/doc/proposal/expected
|
||||
## More C++: https://github.com/ned14/outcome
|
||||
##
|
||||
## Swift is interesting in that it uses a non-exception implementation but
|
||||
## calls errors exceptions and has lots of syntactic sugar to make them feel
|
||||
## that way by implicitly passing them up the call chain - with a mandatory
|
||||
## annotation that function may throw:
|
||||
## https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/ErrorHandling.html
|
||||
##
|
||||
## # Considerations for the error type
|
||||
##
|
||||
## * Use a `string` or a `cstring` if you want to provide a diagnostic for
|
||||
## the caller without an expectation that they will differentiate between
|
||||
## different errors. Callers should never parse the given string!
|
||||
## * Use an `enum` to provide in-depth errors where the caller is expected
|
||||
## to have different logic for different errors
|
||||
## * Use a complex type to include error-specific meta-data - or make the
|
||||
## meta-data collection a visible part of your API in another way - this
|
||||
## way it remains discoverable by the caller!
|
||||
##
|
||||
## A natural "error API" progression is starting with `Option[T]`, then
|
||||
## `Result[T, cstring]`, `Result[T, enum]` and `Result[T, object]` in
|
||||
## escalating order of complexity.
|
||||
##
|
||||
## # Other implemenations in nim
|
||||
##
|
||||
## There are other implementations in nim that you might prefer:
|
||||
## * Either from nimfp: https://github.com/vegansk/nimfp/blob/master/src/fp/either.nim
|
||||
## * result_type: https://github.com/kapralos/result_type/
|
||||
##
|
||||
## # Implementation notes
|
||||
##
|
||||
## This implementation is mostly based on the one in rust. Compared to it,
|
||||
## there are a few differences - if know of creative ways to improve things,
|
||||
## I'm all ears.
|
||||
##
|
||||
## * Rust has the enum variants which lend themselves to nice construction
|
||||
## where the full Result type isn't needed: `Err("some error")` doesn't
|
||||
## need to know value type - maybe some creative converter or something
|
||||
## can deal with this?
|
||||
## * Nim templates allow us to fail fast without extra effort, meaning the
|
||||
## other side of `and`/`or` isn't evaluated unless necessary - nice!
|
||||
## * Rust uses From traits to deal with result translation as the result
|
||||
## travels up the call stack - needs more tinkering - some implicit
|
||||
## conversions would be nice here
|
||||
## * Pattern matching in rust allows convenient extraction of value or error
|
||||
## in one go.
|
||||
##
|
||||
## # Performance considerations
|
||||
##
|
||||
## When returning a Result instead of a simple value, there are a few things
|
||||
## to take into consideration - in general, we are returning more
|
||||
## information directly to the caller which has an associated cost.
|
||||
##
|
||||
## Result is a value type, thus its performance characteristics
|
||||
## generally follow the performance of copying the value or error that
|
||||
## it stores. `Result` would benefit greatly from "move" support in the
|
||||
## language.
|
||||
##
|
||||
## In many cases, these performance costs are negligeable, but nonetheless
|
||||
## they are important to be aware of, to structure your code in an efficient
|
||||
## manner:
|
||||
##
|
||||
## * Memory overhead
|
||||
## Result is stored in memory as a union with a `bool` discriminator -
|
||||
## alignment makes it somewhat tricky to give an exact size, but in
|
||||
## general, `Result[int, int]` will take up `2*sizeof(int)` bytes:
|
||||
## 1 `int` for the discriminator and padding, 1 `int` for either the value
|
||||
## or the error. The additional size means that returning may take up more
|
||||
## registers or spill onto the stack.
|
||||
## * Loss of RVO
|
||||
## Nim does return-value-optimization by rewriting `proc f(): X` into
|
||||
## `proc f(result: var X)` - in an expression like `let x = f()`, this
|
||||
## allows it to avoid a copy from the "temporary" return value to `x` -
|
||||
## when using Result, this copy currently happens always because you need
|
||||
## to fetch the value from the Result in a second step: `let x = f().value`
|
||||
## * Extra copies
|
||||
## To avoid spurious evaluation of expressions in templates, we use a
|
||||
## temporary variable sometimes - this means an unnecessary copy for some
|
||||
## types.
|
||||
## * Bad codegen
|
||||
## When doing RVO, Nim generates poor and slow code: it uses a construct
|
||||
## called `genericReset` that will zero-initialize a value using dynamic
|
||||
## RTTI - a process that the C compiler subsequently is unable to
|
||||
## optimize. This applies to all types, but is exacerbated with Result
|
||||
## because of its bigger footprint - this should be fixed in compiler.
|
||||
## * Double zero-initialization bug
|
||||
## Nim has an initialization bug that causes additional poor performance:
|
||||
## `var x = f()` will be expanded into `var x; zeroInit(x); f(x)` where
|
||||
## `f(x)` will call the slow `genericReset` and zero-init `x` again,
|
||||
## unnecessarily.
|
||||
##
|
||||
## Comparing `Result` performance to exceptions in Nim is difficult - it
|
||||
## will depend on the error type used, the frequency at which exceptions
|
||||
## happen, the amount of error handling code in the application and the
|
||||
## compiler and backend used.
|
||||
##
|
||||
## * the default C backend in nim uses `setjmp` for exception handling -
|
||||
## the relative performance of the happy path will depend on the structure
|
||||
## of the code: how many exception handlers there are, how much unwinding
|
||||
## happens. `setjmp` works by taking a snapshot of the full CPU state and
|
||||
## saving it to memory when enterting a try block (or an implict try
|
||||
## block, such as is introduced with `defer` and similar constructs).
|
||||
## * an efficient exception handling mechanism (like the C++ backend or
|
||||
## `nlvm`) will usually have a lower cost on the happy path because the
|
||||
## value can be returned more efficiently. However, there is still a code
|
||||
## and data size increase depending on the specific situation, as well as
|
||||
## loss of optimization opportunities to consider.
|
||||
## * raising an exception is usually (a lot) slower than returning an error
|
||||
## through a Result - at raise time, capturing a call stack and allocating
|
||||
## memory for the Exception is expensive, so the performance difference
|
||||
## comes down to the complexity of the error type used.
|
||||
## * checking for errors with Result is local branching operation that also
|
||||
## happens on the happy path - this may be a cost.
|
||||
##
|
||||
## An accurate summary might be that Exceptions are at its most efficient
|
||||
## when errors are not handled and don't happen.
|
||||
##
|
||||
## # Relevant nim bugs
|
||||
##
|
||||
## https://github.com/nim-lang/Nim/issues/13799 - type issues
|
||||
## https://github.com/nim-lang/Nim/issues/8745 - genericReset slow
|
||||
## https://github.com/nim-lang/Nim/issues/13879 - double-zero-init slow
|
||||
## https://github.com/nim-lang/Nim/issues/14318 - generic error raises pragma
|
||||
|
||||
case o: bool
|
||||
of false:
|
||||
e: E
|
||||
of true:
|
||||
v: T
|
||||
|
||||
Opt*[T] = Result[T, void]
|
||||
|
||||
func raiseResultError[T, E](self: Result[T, E]) {.noreturn, noinline.} =
|
||||
# noinline because raising should take as little space as possible at call
|
||||
# site
|
||||
mixin toException
|
||||
|
||||
when E is ref Exception:
|
||||
if self.e.isNil: # for example Result.default()!
|
||||
raise (ref ResultError[void])(msg: "Trying to access value with err (nil)")
|
||||
raise self.e
|
||||
elif compiles(toException(self.e)):
|
||||
raise toException(self.e)
|
||||
elif compiles($self.e):
|
||||
raise (ref ResultError[E])(
|
||||
error: self.e, msg: "Trying to access value with err: " & $self.e)
|
||||
else:
|
||||
raise (res ResultError[E])(msg: "Trying to access value with err", error: self.e)
|
||||
|
||||
func raiseResultDefect(m: string, v: auto) {.noreturn, noinline.} =
|
||||
mixin `$`
|
||||
when compiles($v): raise (ref ResultDefect)(msg: m & ": " & $v)
|
||||
else: raise (ref ResultDefect)(msg: m)
|
||||
|
||||
func raiseResultDefect(m: string) {.noreturn, noinline.} =
|
||||
raise (ref ResultDefect)(msg: m)
|
||||
|
||||
template assertOk(self: Result) =
|
||||
if not self.o:
|
||||
when self.E isnot void:
|
||||
raiseResultDefect("Trying to acces value with err Result", self.e)
|
||||
else:
|
||||
raiseResultDefect("Trying to acces value with err Result")
|
||||
|
||||
template ok*[T, E](R: type Result[T, E], x: auto): R =
|
||||
## Initialize a result with a success and value
|
||||
## Example: `Result[int, string].ok(42)`
|
||||
R(o: true, v: x)
|
||||
|
||||
template ok*[T, E](self: var Result[T, E], x: auto) =
|
||||
## Set the result to success and update value
|
||||
## Example: `result.ok(42)`
|
||||
self = ok(type self, x)
|
||||
|
||||
template err*[T, E](R: type Result[T, E], x: auto): R =
|
||||
## Initialize the result to an error
|
||||
## Example: `Result[int, string].err("uh-oh")`
|
||||
R(o: false, e: x)
|
||||
|
||||
template err*[T](R: type Result[T, void]): R =
|
||||
R(o: false)
|
||||
|
||||
template err*[T, E](self: var Result[T, E], x: auto) =
|
||||
## Set the result as an error
|
||||
## Example: `result.err("uh-oh")`
|
||||
self = err(type self, x)
|
||||
|
||||
template err*[T](self: var Result[T, void]) =
|
||||
## Set the result as an error
|
||||
## Example: `result.err()`
|
||||
self = err(type self)
|
||||
|
||||
template ok*(v: auto): auto = ok(typeof(result), v)
|
||||
template err*(v: auto): auto = err(typeof(result), v)
|
||||
|
||||
template isOk*(self: Result): bool = self.o
|
||||
template isErr*(self: Result): bool = not self.o
|
||||
|
||||
template isSome*(o: Opt): bool =
|
||||
## Alias for `isOk`
|
||||
isOk o
|
||||
|
||||
template isNone*(o: Opt): bool =
|
||||
## Alias of `isErr`
|
||||
isErr o
|
||||
|
||||
func map*[T, E, A](
|
||||
self: Result[T, E], f: proc(x: T): A): Result[A, E] {.inline.} =
|
||||
## Transform value using f, or return error
|
||||
##
|
||||
## ```
|
||||
## let r = Result[int, cstring).ok(42)
|
||||
## assert r.map(proc (v: int): int = $v).get() == "42"
|
||||
## ```
|
||||
if self.o: result.ok(f(self.v))
|
||||
else: result.err(self.e)
|
||||
|
||||
func flatMap*[T, E, A](
|
||||
self: Result[T, E], f: proc(x: T): Result[A, E]): Result[A, E] {.inline.} =
|
||||
if self.o: f(self.v)
|
||||
else: Result[A, E].err(self.e)
|
||||
|
||||
func mapErr*[T: not void, E, A](
|
||||
self: Result[T, E], f: proc(x: E): A): Result[T, A] {.inline.} =
|
||||
## Transform error using f, or return value
|
||||
if self.o: result.ok(self.v)
|
||||
else: result.err(f(self.e))
|
||||
|
||||
func mapConvert*[T0, E0](
|
||||
self: Result[T0, E0], T1: type): Result[T1, E0] {.inline.} =
|
||||
## Convert result value to A using an conversion
|
||||
# Would be nice if it was automatic...
|
||||
if self.o: result.ok(T1(self.v))
|
||||
else: result.err(self.e)
|
||||
|
||||
func mapCast*[T0, E0](
|
||||
self: Result[T0, E0], T1: type): Result[T1, E0] {.inline.} =
|
||||
## Convert result value to A using a cast
|
||||
## Would be nice with nicer syntax...
|
||||
if self.o: result.ok(cast[T1](self.v))
|
||||
else: result.err(self.e)
|
||||
|
||||
template `and`*[T0, E, T1](self: Result[T0, E], other: Result[T1, E]): Result[T1, E] =
|
||||
## Evaluate `other` iff self.isOk, else return error
|
||||
## fail-fast - will not evaluate other if a is an error
|
||||
let s = self
|
||||
if s.o:
|
||||
other
|
||||
else:
|
||||
when type(self) is type(other):
|
||||
s
|
||||
else:
|
||||
type R = type(other)
|
||||
err(R, s.e)
|
||||
|
||||
template `or`*[T, E0, E1](self: Result[T, E0], other: Result[T, E1]): Result[T, E1] =
|
||||
## Evaluate `other` iff `not self.isOk`, else return `self`
|
||||
## fail-fast - will not evaluate `other` if `self` is ok
|
||||
##
|
||||
## ```
|
||||
## func f(): Result[int, SomeEnum] =
|
||||
## f2() or err(EnumValue) # Collapse errors from other module / function
|
||||
## ```
|
||||
let s = self
|
||||
if s.o:
|
||||
when type(self) is type(other):
|
||||
s
|
||||
else:
|
||||
type R = type(other)
|
||||
ok(R, s.v)
|
||||
else:
|
||||
other
|
||||
|
||||
template catch*(body: typed): Result[type(body), ref CatchableError] =
|
||||
## Catch exceptions for body and store them in the Result
|
||||
##
|
||||
## ```
|
||||
## let r = catch: someFuncThatMayRaise()
|
||||
## ```
|
||||
type R = Result[type(body), ref CatchableError]
|
||||
|
||||
try:
|
||||
R.ok(body)
|
||||
except CatchableError as e:
|
||||
R.err(e)
|
||||
|
||||
template capture*[E: Exception](T: type, someExceptionExpr: ref E): Result[T, ref E] =
|
||||
## Evaluate someExceptionExpr and put the exception into a result, making sure
|
||||
## to capture a call stack at the capture site:
|
||||
##
|
||||
## ```
|
||||
## let e: Result[void, ValueError] = void.capture((ref ValueError)(msg: "test"))
|
||||
## echo e.error().getStackTrace()
|
||||
## ```
|
||||
type R = Result[T, ref E]
|
||||
|
||||
var ret: R
|
||||
try:
|
||||
# TODO is this needed? I think so, in order to grab a call stack, but
|
||||
# haven't actually tested...
|
||||
if true:
|
||||
# I'm sure there's a nicer way - this just works :)
|
||||
raise someExceptionExpr
|
||||
except E as caught:
|
||||
ret = R.err(caught)
|
||||
ret
|
||||
|
||||
func `==`*[T0, E0, T1, E1](lhs: Result[T0, E0], rhs: Result[T1, E1]): bool {.inline.} =
|
||||
if lhs.o != rhs.o:
|
||||
false
|
||||
elif lhs.o: # and rhs.o implied
|
||||
lhs.v == rhs.v
|
||||
else:
|
||||
lhs.e == rhs.e
|
||||
|
||||
func get*[T: not void, E](self: Result[T, E]): T {.inline.} =
|
||||
## Fetch value of result if set, or raise Defect
|
||||
## Exception bridge mode: raise given Exception instead
|
||||
## See also: Option.get
|
||||
assertOk(self)
|
||||
self.v
|
||||
|
||||
func tryGet*[T: not void, E](self: Result[T, E]): T {.inline.} =
|
||||
## Fetch value of result if set, or raise
|
||||
## When E is an Exception, raise that exception - otherwise, raise a ResultError[E]
|
||||
mixin raiseResultError
|
||||
if not self.o: self.raiseResultError()
|
||||
self.v
|
||||
|
||||
func get*[T, E](self: Result[T, E], otherwise: T): T {.inline.} =
|
||||
## Fetch value of result if set, or return the value `otherwise`
|
||||
## See `valueOr` for a template version that avoids evaluating `otherwise`
|
||||
## unless necessary
|
||||
if self.o: self.v
|
||||
else: otherwise
|
||||
|
||||
func get*[T, E](self: var Result[T, E]): var T {.inline.} =
|
||||
## Fetch value of result if set, or raise Defect
|
||||
## Exception bridge mode: raise given Exception instead
|
||||
## See also: Option.get
|
||||
assertOk(self)
|
||||
self.v
|
||||
|
||||
template `[]`*[T: not void, E](self: Result[T, E]): T =
|
||||
## Fetch value of result if set, or raise Defect
|
||||
## Exception bridge mode: raise given Exception instead
|
||||
mixin get
|
||||
self.get()
|
||||
|
||||
template `[]`*[T, E](self: var Result[T, E]): var T =
|
||||
## Fetch value of result if set, or raise Defect
|
||||
## Exception bridge mode: raise given Exception instead
|
||||
mixin get
|
||||
self.get()
|
||||
|
||||
template unsafeGet*[T, E](self: Result[T, E]): T =
|
||||
## Fetch value of result if set, undefined behavior if unset
|
||||
## See also: Option.unsafeGet
|
||||
assert self.o
|
||||
|
||||
self.v
|
||||
|
||||
func expect*[T: not void, E](self: Result[T, E], m: string): T =
|
||||
## Return value of Result, or raise a `Defect` with the given message - use
|
||||
## this helper to extract the value when an error is not expected, for example
|
||||
## because the program logic dictates that the operation should never fail
|
||||
##
|
||||
## ```nim
|
||||
## let r = Result[int, int].ok(42)
|
||||
## # Put here a helpful comment why you think this won't fail
|
||||
## echo r.expect("r was just set to ok(42)")
|
||||
## ```
|
||||
if not self.o:
|
||||
raiseResultDefect(m, self.e)
|
||||
self.v
|
||||
|
||||
func expect*[T: not void, E](self: var Result[T, E], m: string): var T =
|
||||
if not self.o:
|
||||
raiseResultDefect(m, self.e)
|
||||
self.v
|
||||
|
||||
func `$`*(self: Result): string =
|
||||
## Returns string representation of `self`
|
||||
if self.o: "Ok(" & $self.v & ")"
|
||||
else: "Err(" & $self.e & ")"
|
||||
|
||||
func error*[T, E](self: Result[T, E]): E =
|
||||
## Fetch error of result if set, or raise Defect
|
||||
if self.o:
|
||||
when T is not void:
|
||||
raiseResultDefect("Trying to access error when value is set", self.v)
|
||||
else:
|
||||
raise (ref ResultDefect)(msg: "Trying to access error when value is set")
|
||||
self.e
|
||||
|
||||
template value*[T, E](self: Result[T, E]): T =
|
||||
mixin get
|
||||
self.get()
|
||||
|
||||
template value*[T, E](self: var Result[T, E]): T =
|
||||
mixin get
|
||||
self.get()
|
||||
|
||||
template valueOr*[T, E](self: Result[T, E], def: T): T =
|
||||
## Fetch value of result if set, or supplied default
|
||||
## default will not be evaluated iff value is set
|
||||
if self.o: self.v
|
||||
else: def
|
||||
|
||||
# void support
|
||||
|
||||
template ok*[E](R: type Result[void, E]): auto =
|
||||
## Initialize a result with a success and value
|
||||
## Example: `Result[int, string].ok(42)`
|
||||
R(o: true)
|
||||
|
||||
template ok*[E](self: var Result[void, E]) =
|
||||
## Set the result to success and update value
|
||||
## Example: `result.ok(42)`
|
||||
mixin ok
|
||||
self = (type self).ok()
|
||||
|
||||
template ok*(): auto =
|
||||
mixin ok
|
||||
ok(typeof(result))
|
||||
|
||||
template err*(): auto =
|
||||
mixin err
|
||||
err(typeof(result))
|
||||
|
||||
# TODO:
|
||||
# Supporting `map` and `get` operations on a `void` result is quite
|
||||
# an unusual API. We should provide some motivating examples.
|
||||
|
||||
func map*[E, A](
|
||||
self: Result[void, E], f: proc(): A): Result[A, E] {.inline.} =
|
||||
## Transform value using f, or return error
|
||||
if self.o: result.ok(f())
|
||||
else: result.err(self.e)
|
||||
|
||||
func flatMap*[E, A](
|
||||
self: Result[void, E], f: proc(): Result[A, E]): Result[A, E] {.inline.} =
|
||||
if self.o: f(self.v)
|
||||
else: Result[A, E].err(self.e)
|
||||
|
||||
func mapErr*[E, A](
|
||||
self: Result[void, E], f: proc(x: E): A): Result[void, A] {.inline.} =
|
||||
## Transform error using f, or return value
|
||||
if self.o: result.ok()
|
||||
else: result.err(f(self.e))
|
||||
|
||||
func map*[T, E](
|
||||
self: Result[T, E], f: proc(x: T)): Result[void, E] {.inline.} =
|
||||
## Transform value using f, or return error
|
||||
if self.o: f(self.v); result.ok()
|
||||
else: result.err(self.e)
|
||||
|
||||
func get*[E](self: Result[void, E]) {.inline.} =
|
||||
## Fetch value of result if set, or raise
|
||||
## See also: Option.get
|
||||
mixin assertOk
|
||||
assertOk(self)
|
||||
|
||||
func tryGet*[E](self: Result[void, E]) {.inline.} =
|
||||
## Fetch value of result if set, or raise a CatchableError
|
||||
mixin raiseResultError
|
||||
if not self.o:
|
||||
self.raiseResultError()
|
||||
|
||||
template `[]`*[E](self: Result[void, E]) =
|
||||
## Fetch value of result if set, or raise
|
||||
mixin get
|
||||
self.get()
|
||||
|
||||
template unsafeGet*[E](self: Result[void, E]) =
|
||||
## Fetch value of result if set, undefined behavior if unset
|
||||
## See also: Option.unsafeGet
|
||||
assert self.o
|
||||
|
||||
func expect*[E](self: Result[void, E], msg: string) =
|
||||
if not self.o:
|
||||
raise (ref ResultDefect)(msg: msg)
|
||||
|
||||
func `$`*[E](self: Result[void, E]): string =
|
||||
## Returns string representation of `self`
|
||||
if self.o: "Ok()"
|
||||
else: "Err(" & $self.e & ")"
|
||||
|
||||
template value*[E](self: Result[void, E]) =
|
||||
mixin get
|
||||
self.get()
|
||||
|
||||
template value*[E](self: var Result[void, E]) =
|
||||
mixin get
|
||||
self.get()
|
||||
|
||||
template `?`*[T, E](self: Result[T, E]): T =
|
||||
## Early return - if self is an error, we will return from the current
|
||||
## function, else we'll move on..
|
||||
##
|
||||
## ```
|
||||
## let v = ? funcWithResult()
|
||||
## echo v # prints value, not Result!
|
||||
## ```
|
||||
## Experimental
|
||||
# TODO the v copy is here to prevent multiple evaluations of self - could
|
||||
# probably avoid it with some fancy macro magic..
|
||||
let v = (self)
|
||||
if not v.o:
|
||||
when typeof(result) is typeof(v):
|
||||
return v
|
||||
else:
|
||||
return err(typeof(result), v.e)
|
||||
|
||||
v.v
|
||||
42
readme.md
42
readme.md
|
|
@ -1,6 +1,10 @@
|
|||
# nimPNG (PNG + APNG)
|
||||
Portable Network Graphics Encoder and Decoder written in Nim store lossless image with good compression.
|
||||
Since version 0.2.0 also support Animated PNG!
|
||||
|
||||
Notable releases:
|
||||
- 0.2.0 support Animated PNG!
|
||||
- 0.2.6 compile with --gc:arc.
|
||||
- 0.3.0 [new set of API](apidoc.md) using seq[uint8] and new method to handle error.
|
||||
|
||||
[](https://travis-ci.org/jangko/nimPNG)
|
||||
[](https://ci.appveyor.com/project/jangko/nimpng)
|
||||
|
|
@ -9,11 +13,11 @@ Since version 0.2.0 also support Animated PNG!
|
|||
|
||||
all PNG standard color mode are supported:
|
||||
|
||||
- LCT_GREY = 0, # greyscale: 1,2,4,8,16 bit
|
||||
- LCT_RGB = 2, # RGB: 8,16 bit
|
||||
- LCT_PALETTE = 3, # palette: 1,2,4,8 bit
|
||||
- LCT_GREY_ALPHA = 4, # greyscale with alpha: 8,16 bit
|
||||
- LCT_RGBA = 6 # RGB with alpha: 8,16 bit
|
||||
- LCT_GREY = 0, # greyscale: 1,2,4,8,16 bit
|
||||
- LCT_RGB = 2, # RGB: 8,16 bit
|
||||
- LCT_PALETTE = 3, # palette: 1,2,4,8 bit
|
||||
- LCT_GREY_ALPHA = 4, # greyscale with alpha: 8,16 bit
|
||||
- LCT_RGBA = 6 # RGB with alpha: 8,16 bit
|
||||
|
||||
both interlaced and non-interlaced mode supported
|
||||
|
||||
|
|
@ -25,17 +29,17 @@ unknown chunks will be handled properly
|
|||
|
||||
the following chunks are supported (generated/interpreted) by both encoder and decoder:
|
||||
|
||||
- IHDR: header information
|
||||
- PLTE: color palette
|
||||
- IDAT: pixel data
|
||||
- IEND: the final chunk
|
||||
- tRNS: transparency for palettized images
|
||||
- tEXt: textual information
|
||||
- zTXt: compressed textual information
|
||||
- iTXt: international textual information
|
||||
- bKGD: suggested background color
|
||||
- pHYs: physical dimensions
|
||||
- tIME: modification time
|
||||
- IHDR: header information
|
||||
- PLTE: color palette
|
||||
- IDAT: pixel data
|
||||
- IEND: the final chunk
|
||||
- tRNS: transparency for palettized images
|
||||
- tEXt: textual information
|
||||
- zTXt: compressed textual information
|
||||
- iTXt: international textual information
|
||||
- bKGD: suggested background color
|
||||
- pHYs: physical dimensions
|
||||
- tIME: modification time
|
||||
|
||||
the following chunks are parsed correctly, but not used by decoder:
|
||||
cHRM, gAMA, iCCP, sRGB, sBIT, hIST, sPLT
|
||||
|
|
@ -52,7 +56,7 @@ Supported color conversions:
|
|||
- streaming for progressive loading
|
||||
|
||||
## Basic Usage
|
||||
```nimrod
|
||||
```Nim
|
||||
import nimPNG
|
||||
|
||||
let png = loadPNG32("image.png")
|
||||
|
|
@ -66,7 +70,7 @@ let png = loadPNG32("image.png")
|
|||
|
||||
if you already have the whole file in memory:
|
||||
|
||||
```nimrod
|
||||
```Nim
|
||||
let png = decodePNG32(raw_bytes)
|
||||
#will do the same as above
|
||||
```
|
||||
|
|
|
|||
|
|
@ -50,7 +50,7 @@ proc convert(dir: string) =
|
|||
|
||||
proc generateAPNG() =
|
||||
const numFrames = 7
|
||||
var frames: array[numFrames, PNGResult]
|
||||
var frames: array[numFrames, PNGResult[string]]
|
||||
|
||||
for i in 0..<numFrames:
|
||||
frames[i] = loadPNG24("tests" / "apng" / "raw" / "frame" & $i & ".png")
|
||||
|
|
|
|||
|
|
@ -560,7 +560,7 @@ proc testColorKeyConvert() =
|
|||
|
||||
var png = s.decodePNG()
|
||||
var info = png.getInfo()
|
||||
var image2 = png.convert(LCT_RGBA, 8)
|
||||
var image2 = convert(png, LCT_RGBA, 8)
|
||||
|
||||
assertEquals(32 , info.width)
|
||||
assertEquals(32 , info.height)
|
||||
|
|
@ -601,7 +601,7 @@ proc colorConvertTest(bits_in: string, colorType_in: PNGcolorType, bitDepth_in:
|
|||
let modeIn = newColorMode(colorType_in, bitDepth_in)
|
||||
let modeOut = newColorMode(colorType_out, bitDepth_out)
|
||||
var actual = newString(expected.len)
|
||||
convert(
|
||||
convertImpl(
|
||||
actual.toOpenArray(0, actual.len-1),
|
||||
image.toOpenArray(0, image.len-1),
|
||||
modeOut, modeIn, 1)
|
||||
|
|
@ -710,9 +710,9 @@ proc testColorConvert2() =
|
|||
modeOut.colorType = cmb.colorType
|
||||
modeOut.bitDepth = cmb.bitDepth
|
||||
|
||||
convert(input.toOpenArray(0, input.len-1), eight.toOpenArray(0, eight.len-1), modeIn, mode_8, 3 * 3)
|
||||
convert(output.toOpenArray(0, output.len-1), input.toOpenArray(0, input.len-1), modeOut, modeIn, 3 * 3) #Test input to output type
|
||||
convert(eight2.toOpenArray(0, eight2.len-1), output.toOpenArray(0, output.len-1), mode_8, modeOut, 3 * 3)
|
||||
convertImpl(input.toOpenArray(0, input.len-1), eight.toOpenArray(0, eight.len-1), modeIn, mode_8, 3 * 3)
|
||||
convertImpl(output.toOpenArray(0, output.len-1), input.toOpenArray(0, input.len-1), modeOut, modeIn, 3 * 3) #Test input to output type
|
||||
convertImpl(eight2.toOpenArray(0, eight2.len-1), output.toOpenArray(0, output.len-1), mode_8, modeOut, 3 * 3)
|
||||
assertEquals(eight, eight2)
|
||||
|
||||
#tests that there are no crashes with auto color chooser in case of palettes with translucency etc...
|
||||
|
|
@ -759,7 +759,7 @@ proc doRGBAToPaletteTest(palette: openArray[int], expectedType = LCT_PALETTE) =
|
|||
s.setPosition 0
|
||||
var png2 = s.decodePNG()
|
||||
var info = png2.getInfo()
|
||||
var image2 = png2.convert(LCT_RGBA, 8)
|
||||
var image2 = convert(png2, LCT_RGBA, 8)
|
||||
|
||||
assertEquals(image2.data, image)
|
||||
|
||||
|
|
@ -908,7 +908,7 @@ proc testAutoColorModel(colors: string, inbitDepth: int, colorType: PNGcolorType
|
|||
s.setPosition 0
|
||||
var raw = s.decodePNG()
|
||||
var info = raw.getInfo()
|
||||
var decoded = raw.convert(LCT_RGBA, inbitdepth)
|
||||
var decoded = convert(raw, LCT_RGBA, inbitdepth)
|
||||
|
||||
assertEquals(num , info.width)
|
||||
assertEquals(1 , info.height)
|
||||
|
|
|
|||
Loading…
Reference in New Issue