1 files changed, 139 insertions, 0 deletions
diff --git a/tests/misc/tvarnums.nim b/tests/misc/tvarnums.nim
new file mode 100644
index 000000000..498099c49
--- /dev/null
+++ b/tests/misc/tvarnums.nim
@@ -0,0 +1,139 @@
+discard """
+  output: "Success!"
+"""
+# Test variable length binary integers
+
+import
+  strutils
+
+type
+  TBuffer = array[0..10, uint8]
+
+proc toVarNum(x: int32, b: var TBuffer) =
+  # encoding: first bit indicates end of number (0 if at end)
+  # second bit of the first byte denotes the sign (1 --> negative)
+  var a = x
+  if x != low(x):
+    # low(int) is a special case,
+    # because abs() does not work here!
+    # we leave x as it is and use the check >% instead of >
+    # for low(int) this is needed and positive numbers are not affected
+    # anyway
+    a = abs(x)
+  # first 6 bits:
+  b[0] = uint8(ord(a >% 63'i32) shl 7 or (ord(x < 0'i32) shl 6) or (int(a) and 63))
+  a = (a shr 6'i32) and 0x03ffffff # skip first 6 bits
+  var i = 1
+  while a != 0'i32:
+    b[i] = uint8(ord(a >% 127'i32) shl 7 or (int(a) and 127))
+    inc(i)
+    a = a shr 7'i32
+
+proc toVarNum64(x: int64, b: var TBuffer) =
+  # encoding: first bit indicates end of number (0 if at end)
+  # second bit of the first byte denotes the sign (1 --> negative)
+  var a = x
+  if x != low(x):
+    # low(int) is a special case,
+    # because abs() does not work here!
+    # we leave x as it is and use the check >% instead of >
+    # for low(int) this is needed and positive numbers are not affected
+    # anyway
+    a = abs(x)
+  # first 6 bits:
+  b[0] = uint8(ord(a >% 63'i64) shl 7 or (ord(x < 0'i64) shl 6) or int(a and 63))
+  a = (a shr 6) and 0x03ffffffffffffff # skip first 6 bits
+  var i = 1
+  while a != 0'i64:
+    b[i] = uint8(ord(a >% 127'i64) shl 7 or int(a and 127))
+    inc(i)
+    a = a shr 7
+
+proc toNum64(b: TBuffer): int64 =
+  # treat first byte different:
+  result = int64(b[0]) and 63
+  var
+    i = 0
+    Shift = 6'i64
+  while (int(b[i]) and 128) != 0:
+    inc(i)
+    result = result or ((int64(b[i]) and 127) shl Shift)
+    inc(Shift, 7)
+  if (int(b[0]) and 64) != 0: # sign bit set?
+    result = not result +% 1
+    # this is the same as ``- result``
+    # but gives no overflow error for low(int)
+
+proc toNum(b: TBuffer): int32 =
+  # treat first byte different:
+  result = int32(b[0]) and 63
+  var
+    i = 0
+    Shift = 6'i32
+  while (int(b[i]) and 128) != 0:
+    inc(i)
+    result = result or ((int32(b[i]) and 127'i32) shl Shift)
+    Shift = Shift + 7'i32
+  if (int(b[0]) and (1 shl 6)) != 0: # sign bit set?
+    result = (not result) +% 1'i32
+    # this is the same as ``- result``
+    # but gives no overflow error for low(int)
+
+proc toBinary(x: int64): string =
+  result = newString(64)
+  for i in 0..63:
+    result[63-i] = chr((int(x shr i) and 1) + ord('0'))
+
+proc t64(i: int64) =
+  var
+    b: TBuffer
+  toVarNum64(i, b)
+  var x = toNum64(b)
+  if x != i:
+    writeLine(stdout, $i)
+    writeLine(stdout, toBinary(i))
+    writeLine(stdout, toBinary(x))
+
+proc t32(i: int32) =
+  var
+    b: TBuffer
+  toVarNum(i, b)
+  var x = toNum(b)
+  if x != i:
+    writeLine(stdout, toBinary(i))
+    writeLine(stdout, toBinary(x))
+
+proc tm(i: int32) =
+  var
+    b: TBuffer
+  toVarNum64(i, b)
+  var x = toNum(b)
+  if x != i:
+    writeLine(stdout, toBinary(i))
+    writeLine(stdout, toBinary(x))
+
+t32(0)
+t32(1)
+t32(-1)
+t32(-100_000)
+t32(100_000)
+t32(low(int32))
+t32(high(int32))
+
+t64(low(int64))
+t64(high(int64))
+t64(0)
+t64(-1)
+t64(1)
+t64(1000_000)
+t64(-1000_000)
+
+tm(0)
+tm(1)
+tm(-1)
+tm(-100_000)
+tm(100_000)
+tm(low(int32))
+tm(high(int32))
+
+writeLine(stdout, "Success!") #OUT Success!