add support for StringStream read

lib/js/jsarrays.nim

@@ -0,0 +1,78 @@
+##[
+This module provides a wrapper for ArrayBuffer, DataView and related API's such
+as `getInt8`, `setInt16`.
+]##
+
+#[
+`BigInt` could be homed here.
+]#
+
+static: doAssert defined(js)
+
+type
+  ArrayBuffer* = ref object {.importjs.}
+  DataView* = ref object {.importjs.}
+    ## https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView
+
+proc newArrayBuffer*(n: int): ArrayBuffer {.importjs: "new ArrayBuffer(#)".}
+proc newDataView*(a: ArrayBuffer, offset: int): DataView {.importjs: "new DataView(#, #)".}
+proc toArrayBuffer*(a: string): ArrayBuffer =
+  let n = a.len
+  result = newArrayBuffer(n)
+  {.emit:"""
+  const view = new Uint8Array(`result`);
+  for(i=0;i<`n`;i++){
+    view[i] = `a`[i];
+  }
+  """.}
+
+template genGetSet(T, funGet, funSet): untyped =
+  proc funGet(a: DataView, byteOffset: int, littleEndian: bool): T {.importcpp.}
+  proc funSet(a: DataView, byteOffset: int, value: T, littleEndian: bool): T {.importcpp.}
+
+genGetSet int8, getInt8, setInt8
+genGetSet int16, getInt16, setInt16
+genGetSet int32, getInt32, setInt32
+
+proc getTyped*(a: DataView, T: typedesc, offset: int, littleEndian: bool): T =
+  when false: discard
+  elif T is int8: getInt8(a, offset, littleEndian)
+  elif T is int16: getInt16(a, offset, littleEndian)
+  elif T is int32: getInt32(a, offset, littleEndian)
+  else: static doAssert false, $T # add as needed
+
+when false: ## scratch below
+  # view[i] = str.charCodeAt(i); // check whether would be needed for cstring
+
+  # proc `[]=`(a: ArrayBuffer, index: int, val: char) =
+  #   {.emit: """`a`[`index`] = `val`;""".}
+
+  # DataView.prototype.getBigInt64()
+  # DataView.prototype.getBigUint64()
+  # DataView.prototype.getFloat32()
+  # DataView.prototype.getFloat64()
+  # DataView.prototype.getInt16()
+  # DataView.prototype.getInt32()
+  # DataView.prototype.getInt8()
+  # DataView.prototype.getUint16()
+  # DataView.prototype.getUint32()
+  # DataView.prototype.getUint8()
+  # DataView.prototype.setBigInt64()
+  # DataView.prototype.setBigUint64()
+  # DataView.prototype.setFloat32()
+  # DataView.prototype.setFloat64()
+  # DataView.prototype.setInt16()
+  # DataView.prototype.setInt32()
+  # DataView.prototype.setInt8()
+  # DataView.prototype.setUint16()
+  # DataView.prototype.setUint32()
+  # DataView.prototype.setUint8()
+
+  proc decode() =
+    case bufLen
+    of int32.sizeof:
+      cast[ptr int](buffer)[] = s2.getInt32(0, true)
+    of int16.sizeof:
+      cast[ptr int16](buffer)[] = s2.getInt16(0, true)
+    else:
+      doAssert false

lib/pure/streams.nim

@@ -96,6 +96,9 @@
 
 include "system/inclrtl"
 
+when defined(js):
+  import std/jsarrays
+
 const taintMode = compileOption("taintmode")
 
 proc newEIO(msg: string): owned(ref IOError) =
@@ -393,8 +396,6 @@ proc writeLine*(s: Stream, args: varargs[string, `$`]) =
 
 proc read*[T](s: Stream, result: var T) =
   ## Generic read procedure. Reads `result` from the stream `s`.
-  ##
-  ## **Note:** Not available for JS backend. Use `readStr <#readStr,Stream,int>`_ for now.
   runnableExamples:
     var strm = newStringStream("012")
     ## readInt
@@ -412,8 +413,6 @@ proc read*[T](s: Stream, result: var T) =
 
 proc peek*[T](s: Stream, result: var T) =
   ## Generic peek procedure. Peeks `result` from the stream `s`.
-  ##
-  ## **Note:** Not available for JS backend. Use `peekStr <#peekStr,Stream,int>`_ for now.
   runnableExamples:
     var strm = newStringStream("012")
     ## peekInt
@@ -1134,6 +1133,10 @@ type
                   ## This is updated when called `writeLine` etc.
     pos: int
 
+    when defined js:
+      data2: ArrayBuffer
+      dataView: DataView
+
 when (NimMajor, NimMinor) < (1, 3) and defined(js):
   proc ssAtEnd(s: Stream): bool {.compileTime.} =
     var s = StringStream(s)
@@ -1217,11 +1220,19 @@ else: # after 1.3 or JS not defined
     result = min(bufLen, s.data.len - s.pos)
     if result > 0:
       when defined(js):
-        try:
-          cast[ptr string](buffer)[][0..<result] = s.data[s.pos..<s.pos+result]
-        except:
-          raise newException(Defect, "could not read string stream, " &
-            "did you use a non-string buffer pointer?", getCurrentException())
+        let view = s.dataView
+        template fun(T) =
+          cast[ptr T](buffer)[] = view.getTyped(T, 0, true)
+        case bufLen
+        of int8.sizeof: fun(int8)
+        of int32.sizeof: fun(int32)
+        of int16.sizeof: fun(int16)
+        else: doAssert false, $bufLen
+        # try:
+        #   cast[ptr string](buffer)[][0..<result] = s.data[s.pos..<s.pos+result]
+        # except:
+        #   raise newException(Defect, "could not read string stream, " &
+        #     "did you use a non-string buffer pointer?", getCurrentException())
       elif not defined(nimscript):
         copyMem(buffer, addr(s.data[s.pos]), result)
       inc(s.pos, result)
@@ -1285,6 +1296,10 @@ else: # after 1.3 or JS not defined
 
     new(result)
     result.data = s
+    when defined js:
+      # IMPROVE, move
+      result.data2 = s.toArrayBuffer
+      result.dataView = newDataView(result.data2, 0)
     result.pos = 0
     result.closeImpl = ssClose
     result.atEndImpl = ssAtEnd

tests/js/tstreams.nim

@@ -8,15 +8,39 @@ GROOT
 
 import streams
 
-var s = newStringStream("I\nAM\nGROOT")
-doAssert s.peekStr(1) == "I"
-doAssert s.peekChar() == 'I'
-for line in s.lines:
-  echo line
-s.close
+block:
+  var s = newStringStream("I\nAM\nGROOT")
+  doAssert s.peekStr(1) == "I"
+  doAssert s.peekChar() == 'I'
+  for line in s.lines:
+    echo line
+  s.close
 
-var s2 = newStringStream("abc")
-doAssert s2.readAll == "abc"
-s2.write("def")
-doAssert s2.data == "abcdef"
-s2.close
+  var s2 = newStringStream("abc")
+  doAssert s2.readAll == "abc"
+  s2.write("def")
+  doAssert s2.data == "abcdef"
+  s2.close
+
+
+block:
+  proc fun[T](x: T) =
+    # todo: this could be done via `write` on a StringStream
+    var str: string
+    str.setLen 10
+    for i in 0..<T.sizeof: # improve
+      str[i] = cast[char](255 and (x shr (i*8)))
+
+    var s = newStringStream(str)
+    var x2: T
+    s.read(x2)
+    doAssert x2 == x
+    # echo (x, x2)
+
+  fun(234_560.int32)
+  fun(234.int16)
+  fun(0.int16)
+  fun(12.uint8)
+  fun(123123.int32)
+  fun(123123.uint32)
+  fun((-123).int8)