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if not modules then modules = { } end modules ['util-sac'] = {
version = 1.001,
comment = "companion to luat-lib.mkiv",
author = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
copyright = "PRAGMA ADE / ConTeXt Development Team",
license = "see context related readme files"
}
-- experimental string access (some 3 times faster than file access when messing
-- with bytes)
local byte, sub = string.byte, string.sub
local extract = bit32.extract
utilities = utilities or { }
local streams = { }
utilities.streams = streams
function streams.open(filename,zerobased)
local f = io.loaddata(filename)
return { f, 1, #f, zerobased or false }
end
function streams.close()
-- dummy
end
function streams.size(f)
return f and f[3] or 0
end
function streams.setposition(f,i)
if f[4] then
-- zerobased
if i <= 0 then
f[2] = 1
else
f[2] = i + 1
end
else
if i <= 1 then
f[2] = 1
else
f[2] = i
end
end
end
function streams.getposition(f)
if f[4] then
-- zerobased
return f[2] - 1
else
return f[2]
end
end
function streams.look(f,n,chars)
local b = f[2]
local e = b + n - 1
if chars then
return sub(f[1],b,e)
else
return byte(f[1],b,e)
end
end
function streams.skip(f,n)
f[2] = f[2] + n
end
function streams.readbyte(f)
local i = f[2]
f[2] = i + 1
return byte(f[1],i)
end
function streams.readbytes(f,n)
local i = f[2]
local j = i + n
f[2] = j
return byte(f[1],i,j-1)
end
function streams.skipbytes(f,n)
f[2] = f[2] + n
end
function streams.readchar(f)
local i = f[2]
f[2] = i + 1
return sub(f[1],i,i)
end
function streams.readstring(f,n)
local i = f[2]
local j = i + n
f[2] = j
return sub(f[1],i,j-1)
end
function streams.readinteger1(f) -- one byte
local i = f[2]
f[2] = i + 1
local n = byte(f[1],i)
if n >= 0x80 then
return n - 0xFF - 1
else
return n
end
end
streams.readcardinal1 = streams.readbyte -- one byte
streams.readcardinal = streams.readcardinal1
streams.readinteger = streams.readinteger1
function streams.readcardinal2(f)
local i = f[2]
local j = i + 1
f[2] = j + 1
local a, b = byte(f[1],i,j)
return 0x100 * a + b
end
function streams.readinteger2(f)
local i = f[2]
local j = i + 1
f[2] = j + 1
local a, b = byte(f[1],i,j)
local n = 0x100 * a + b
if n >= 0x8000 then
return n - 0xFFFF - 1
else
return n
end
end
function streams.readcardinal3(f)
local i = f[2]
local j = i + 2
f[2] = j + 1
local a, b, c = byte(f[1],i,j)
return 0x10000 * a + 0x100 * b + c
end
function streams.readcardinal4(f)
local i = f[2]
local j = i + 3
f[2] = j + 1
local a, b, c, d = byte(f[1],i,j)
return 0x1000000 * a + 0x10000 * b + 0x100 * c + d
end
function streams.readinteger4(f)
local i = f[2]
local j = i + 3
f[2] = j + 1
local a, b, c, d = byte(f[1],i,j)
local n = 0x1000000 * a + 0x10000 * b + 0x100 * c + d
if n >= 0x8000000 then
return n - 0xFFFFFFFF - 1
else
return n
end
end
function streams.readfixed4(f)
local i = f[2]
local j = i + 3
f[2] = j + 1
local a, b, c, d = byte(f[1],i,j)
local n = 0x100 * a + b
if n >= 0x8000 then
return n - 0xFFFF - 1 + (0x100 * c + d)/0xFFFF
else
return n + (0x100 * c + d)/0xFFFF
end
end
function streams.read2dot14(f)
local i = f[2]
local j = i + 1
f[2] = j + 1
local a, b = byte(f[1],i,j)
local n = 0x100 * a + b
local m = extract(n,0,30)
if n > 0x7FFF then
n = extract(n,30,2)
return m/0x4000 - 4
else
n = extract(n,30,2)
return n + m/0x4000
end
end
function streams.skipshort(f,n)
f[2] = f[2] + 2*(n or 1)
end
function streams.skiplong(f,n)
f[2] = f[2] + 4*(n or 1)
end
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