1 files changed, 202 insertions, 0 deletions
diff --git a/tex/context/base/mkiv/util-sac.lua b/tex/context/base/mkiv/util-sac.lua
new file mode 100644
index 000000000..8a12e7cf0
--- /dev/null
+++ b/tex/context/base/mkiv/util-sac.lua
@@ -0,0 +1,202 @@
+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