serialize the most recently used blitbuffer/koptcontext

to speedup koreader startup for PDF/DJVU documents
especially when reflowing

frontend/memutils.lua

@@ -0,0 +1,131 @@
+local ffi = require "ffi"
+local bit = require "bit"
+local band = bit.band
+local bor = bit.bor
+local rshift = bit.rshift
+local lshift = bit.lshift
+
+
+
+
+ffi.cdef[[
+void * malloc ( size_t size );
+void free ( void * ptr );
+void * realloc ( void * ptr, size_t size );
+]]
+
+function bzero(dest, nbytes)
+	ffi.fill(dest, nbytes)
+	return dest
+end
+
+function bcopy(src, dest, nbytes)
+	ffi.copy(dest, src, nbytes)
+end
+
+function bcmp(ptr1, ptr2, nbytes)
+	for i=0,nbytes do
+		if ptr1[i] ~= ptr2[i] then return -1 end
+	end
+
+	return 0
+end
+
+
+
+function memset(dest, c, len)
+	ffi.fill(dest, len, c)
+	return dest
+end
+
+function memcpy(dest, src, nbytes)
+	ffi.copy(dest, src, nbytes)
+end
+
+function memcmp(ptr1, ptr2, nbytes)
+	local p1 = ffi.cast("const uint8_t *", ptr1)
+	local p2 = ffi.cast("const uint8_t *", ptr2)
+
+	for i=0,nbytes do
+		if p1[i] ~= p2[i] then return -1 end
+	end
+
+	return 0
+end
+
+function memchr(ptr, value, num)
+	local p = ffi.cast("const uint8_t *", ptr)
+	for i=0,num-1 do
+		if p[i] == value then return p+i end
+	end
+
+	return nil
+end
+
+function memmove(dst, src, num)
+	local srcptr = ffi.cast("const uint8_t*", src)
+
+	-- If equal, just return
+	if dst == srcptr then return dst end
+
+
+	if srcptr < dst then
+		-- copy from end
+		for i=num-1,0, -1 do
+			dst[i] = srcptr[i];
+		end
+	else
+		-- copy from beginning
+		for i=0,num-1 do
+			dst[i] = srcptr[i];
+		end
+	end
+	return dst
+end
+
+local function memreverse(buff, bufflen)
+	local i = 0;
+	local tmp
+
+	while (i < (bufflen)/2) do
+		tmp = buff[i];
+		buff[i] = buff[bufflen-i-1];
+		buff[bufflen-i-1] = tmp;
+
+		i = i + 1;
+	end
+	return buff
+end
+
+local function getreverse(src, len)
+	if not len then
+		if type(src) == "string" then
+			len = #src
+		else
+			return nil, "unknown length"
+		end
+	end
+
+	local srcptr = ffi.cast("const uint8_t *", src);
+	local dst = ffi.new("uint8_t[?]", len)
+
+	for i = 0, len-1 do
+		dst[i] = srcptr[len-1-i];
+	end
+
+	return dst, len
+end
+
+return {
+	bcmp = bcmp,
+	bcopy = bcopy,
+	bzero = bzero,
+
+	memchr = memchr,
+	memcpy = memcpy,
+	memcmp = memcmp,
+	memmove = memmove,
+	memset = memset,
+
+	memreverse = memreverse,
+}