Utilities for validating ethereum values

tests/ethutils.nim

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+template stripLeadingZeros(value: string): string =
+  var cidx = 0
+  # ignore the last character so we retain '0' on zero value
+  while cidx < value.len - 1 and value[cidx] == '0':
+    cidx.inc
+  value[cidx .. ^1]
+
+proc encodeQuantity*(value: SomeUnsignedInt): string =
+  var hValue = value.toHex.stripLeadingZeros
+  result = "0x" & hValue
+
+template hasHexHeader*(value: string): bool =
+  if value[0] == '0' and value[1] in {'x', 'X'} and value.len > 2: true
+  else: false
+
+template isHexChar*(c: char): bool =
+  if  c notin {'0'..'9'} and
+      c notin {'a'..'f'} and
+      c notin {'A'..'F'}: false
+  else: true
+
+proc validateHexQuantity*(value: string): bool =
+  if not value.hasHexHeader:
+    return false
+  # No leading zeros
+  if value[2] == '0': return false
+  for i in 2..<value.len:
+    let c = value[i]
+    if not c.isHexChar:
+      return false
+  return true
+
+proc validateHexData*(value: string): bool =
+  if not value.hasHexHeader:
+    return false
+  # Leading zeros are allowed
+  for i in 2..<value.len:
+    let c = value[i]
+    if not c.isHexChar:
+      return false
+  # Must be even number of digits
+  if value.len mod 2 != 0: return false
+  return true