2021-08-23 20:05:02 (UTC-03:00)

Marcel Rodrigues <marcelgmr@gmail.com>

move binary input/output to bio.lua

diff --git a/bio.lua b/bio.lua
new file mode 100644
index 0000000..73f3c5c
--- /dev/null
+++ b/bio.lua
@@ -0,0 +1,74 @@
+-- binary input/output
+
+local ffi = require "ffi"
+local bit = require "bit"
+
+local function read_byte(fp)
+    return fp:read(1):byte(1)
+end
+
+local function read_leu16(fp)
+    return read_byte(fp) + bit.lshift(read_byte(fp), 8)
+end
+
+local function read_leu32(fp)
+    return read_leu16(fp) + bit.lshift(read_leu16(fp), 16)
+end
+
+local function read_beu16(fp)
+    return bit.lshift(read_byte(fp), 8) + read_byte(fp)
+end
+
+local function read_beu32(fp)
+    return bit.lshift(read_beu16(fp), 16) + read_beu16(fp)
+end
+
+local function signed(u, nbits)
+    local p = 2^(nbits-1)
+    if u >= p then u = u - p - p end
+    return u
+end
+
+local function read_lei16(fp)
+    return signed(read_leu16(fp), 16)
+end
+
+local function read_lei32(fp)
+    return signed(read_leu32(fp), 32)
+end
+
+local function read_bei16(fp)
+    return signed(read_beu16(fp), 16)
+end
+
+local function read_bei32(fp)
+    return signed(read_beu32(fp), 32)
+end
+
+local function read_led64(fp)
+    return ffi.cast("double *", ffi.new("char[8]", fp:read(8)))[0]
+end
+
+local function write_beu16(fp, n)
+    fp:write(string.char(bit.rshift(n, 8), bit.band(n, 0xFF)))
+end
+
+local function write_beu32(fp, n)
+    write_beu16(fp, bit.rshift(n, 16))
+    write_beu16(fp, bit.band(n, 0xFFFF))
+end
+
+local function write_bei16(fp, n)
+    if n < 0 then
+        n = n + 0x10000
+    end
+    write_beu16(fp, n)
+end
+
+return {
+    read_byte=read_byte, read_leu16=read_leu16, read_leu32=read_leu32,
+    read_beu16=read_beu16, read_beu32=read_beu32, read_lei16=read_lei16,
+    read_lei32=read_lei32, read_bei16=read_bei16, read_bei32=read_bei32,
+    read_led64=read_led64, write_beu16=write_beu16, write_beu32=write_beu32,
+    write_bei16=write_bei16
+}