Created
February 2, 2017 03:27
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exports (main) | |
def mask(width :Int) :Int as DeepFrozen: | |
return (1 << width) - 1 | |
def shift(i :Int, offset :Int, width :Int) :Int as DeepFrozen: | |
return (i >> offset) & mask(width) | |
def makePointer(i :Int) as DeepFrozen: | |
return switch (i & 0x3): | |
match ==0x0: | |
object structPointer: | |
to type() :Str: | |
return "struct" | |
to offset() :Int: | |
return shift(i, 2, 30) | |
to data() :Int: | |
return shift(i, 32, 16) | |
to pointers() :Int: | |
return shift(i, 48, 16) | |
match ==0x1: | |
object listPointer: | |
to type() :Str: | |
return "list" | |
to offset() :Int: | |
return shift(i, 2, 30) | |
to elementType() :Int: | |
return shift(i, 32, 3) | |
to size() :Int: | |
return shift(i, 35, 29) | |
match ==0x2: | |
object farPointer: | |
to type() :Str: | |
return "far" | |
to hasWideLandingPad() :Bool: | |
return 1 == shift(i, 2, 1) | |
to offset() :Int: | |
return shift(i, 3, 29) | |
to segment() :Int: | |
return shift(i, 32, 32) | |
match ==0x3 ? (shift(i, 2, 30) == 0x0): | |
object capPointer: | |
to type() :Str: | |
return "cap" | |
to index() :Bool: | |
return shift(i, 32, 32) | |
def makeCapn(bs :Bytes) as DeepFrozen: | |
def get32LE(i :Int) :Int: | |
var acc := 0 | |
for j in (0..!4): | |
acc <<= 8 | |
acc |= bs[i * 4 + (3 - j)] | |
return acc | |
def getWord(i :Int) :Int: | |
var acc := 0 | |
for j in (0..!8): | |
acc <<= 8 | |
acc |= bs[i * 8 + j] | |
return acc | |
def segmentSizes :List[Int] := { | |
def count := get32LE(0) + 1 | |
[for i in (0..!count) get32LE(i + 1)] | |
} | |
def segmentPositions :List[Int] := { | |
def wordPadding := segmentSizes.size() // 2 + 1 | |
def l := [].diverge() | |
var offset := wordPadding | |
for size in (segmentSizes) { | |
l.push(offset) | |
offset += size | |
} | |
l.snapshot() | |
} | |
traceln(`segment sizes $segmentSizes`) | |
traceln(`segment positions $segmentPositions`) | |
return object capn: | |
to root(): | |
return makePointer(getWord(segmentPositions[0])) | |
def main(_argv, => makeFileResource) as DeepFrozen: | |
def handle := makeFileResource("meta.capn") | |
return when (def bs := handle<-getContents()) -> | |
traceln(`Read in ${bs.size()} bytes`) | |
def capn := makeCapn(bs) | |
def root := capn.root() | |
traceln(`root $root`) | |
traceln(`pointer ${root.offset()} ${root.data()} ${root.pointers()}`) | |
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