From b9a37825a3ff94eb3d69b44723f36dfeed573220 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mamy=20Andr=C3=A9-Ratsimbazafy?= <mamy_github@numforge.co>
Date: Sun, 9 Feb 2020 15:38:30 +0100
Subject: [PATCH] COnsistent IO API between fromRawUint and fromHex and add
 fromUint

---
 constantine/io.nim | 25 ++++++++++++++++---------
 tests/test_io.nim  | 16 ++++++++--------
 2 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/constantine/io.nim b/constantine/io.nim
index 8430a58..e02ad15 100644
--- a/constantine/io.nim
+++ b/constantine/io.nim
@@ -20,9 +20,9 @@ import
 #
 # ############################################################
 
-func parseRawUintLE(
-        src: openarray[byte],
-        bits: static int): BigInt[bits] {.inline.}=
+func fromRawUintLE(
+        T: type BigInt,
+        src: openarray[byte]): T =
   ## Parse an unsigned integer from its canonical
   ## little-endian unsigned representation
   ## And store it into a BigInt of size bits
@@ -52,22 +52,29 @@ func parseRawUintLE(
   if acc_len != 0:
     result.limbs[dst_idx] = acc
 
-func parseRawUint*(
+func fromRawUint*(
+        T: type BigInt,
         src: openarray[byte],
-        bits: static int,
-        srcEndianness: static Endianness): BigInt[bits] =
+        srcEndianness: static Endianness): T {.inline.}=
   ## Parse an unsigned integer from its canonical
   ## big-endian or little-endian unsigned representation
-  ## And store it into a BigInt of size bits
+  ## And store it into a BigInt of size `bits`
   ##
   ## CT:
   ##   - no leaks
 
   when srcEndianness == littleEndian:
-    parseRawUintLE(src, bits)
+    fromRawUintLE(T, src)
   else:
     {.error: "Not implemented at the moment".}
 
+func fromUint*(
+        T: type BigInt,
+        src: SomeUnsignedInt): T =
+  ## Parse a regular unsigned integer
+  ## and store it into a BigInt of size `bits`
+  fromRawUint(T, cast[array[sizeof(src), byte]](src), cpuEndian)
+
 # ############################################################
 #
 # Serialising from internal representation to canonical format
@@ -291,7 +298,7 @@ func fromHex*(T: type BigInt, s: string): T =
   hexToPaddedByteArray(s, bytes, littleEndian)
 
   # 2. Convert canonical uint to Big Int
-  result = parseRawUint(bytes, T.bits, littleEndian)
+  result = T.fromRawUint(bytes, littleEndian)
 
 func dumpHex*(big: BigInt, order: static Endianness = bigEndian): string =
   ## Stringify an int to hex.
diff --git a/tests/test_io.nim b/tests/test_io.nim
index afa1467..ae5368d 100644
--- a/tests/test_io.nim
+++ b/tests/test_io.nim
@@ -17,7 +17,7 @@ suite "IO":
     block: # Sanity check
       let x = 0'u64
       let x_bytes = cast[array[8, byte]](x)
-      let big = parseRawUint(x_bytes, 64, cpuEndian)
+      let big = BigInt[64].fromRawUint(x_bytes, cpuEndian)
 
       check:
         T(big.limbs[0]) == 0
@@ -26,7 +26,7 @@ suite "IO":
     block: # 2^63 is properly represented on 2 limbs
       let x = 1'u64 shl 63
       let x_bytes = cast[array[8, byte]](x)
-      let big = parseRawUint(x_bytes, 64, cpuEndian)
+      let big = BigInt[64].fromRawUint(x_bytes, cpuEndian)
 
       check:
         T(big.limbs[0]) == 0
@@ -37,7 +37,7 @@ suite "IO":
       # "Little-endian" - 2^63
       let x = 1'u64 shl 63
       let x_bytes = cast[array[8, byte]](x)
-      let big = parseRawUint(x_bytes, 64, littleEndian) # It's fine even on big-endian platform. We only want the byte-pattern
+      let big = BigInt[64].fromRawUint(x_bytes, littleEndian) # It's fine even on big-endian platform. We only want the byte-pattern
 
       var r_bytes: array[8, byte]
       dumpRawUint(r_bytes, big, littleEndian)
@@ -46,7 +46,7 @@ suite "IO":
     block: # "Little-endian" - single random
       let x = uint64 rand(0..high(int))
       let x_bytes = cast[array[8, byte]](x)
-      let big = parseRawUint(x_bytes, 64, littleEndian) # It's fine even on big-endian platform. We only want the byte-pattern
+      let big = BigInt[64].fromRawUint(x_bytes, littleEndian) # It's fine even on big-endian platform. We only want the byte-pattern
 
       var r_bytes: array[8, byte]
       dumpRawUint(r_bytes, big, littleEndian)
@@ -56,7 +56,7 @@ suite "IO":
       for _ in 0 ..< 10:
         let x = uint64 rand(0..high(int))
         let x_bytes = cast[array[8, byte]](x)
-        let big = parseRawUint(x_bytes, 64, littleEndian) # It's fine even on big-endian platform. We only want the byte-pattern
+        let big = BigInt[64].fromRawUint(x_bytes, littleEndian) # It's fine even on big-endian platform. We only want the byte-pattern
 
         var r_bytes: array[8, byte]
         dumpRawUint(r_bytes, big, littleEndian)
@@ -65,21 +65,21 @@ suite "IO":
   test "Round trip on elliptic curve constants":
     block: # Secp256k1 - https://en.bitcoin.it/wiki/Secp256k1
       const p = "0xfffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f"
-      let x = fromHex(BigInt[256], p)
+      let x = BigInt[256].fromHex(p)
       let hex = x.dumpHex(bigEndian)
 
       check: p == hex
 
     block: # BN254 - https://github.com/ethereum/py_ecc/blob/master/py_ecc/fields/field_properties.py
       const p = "0x30644e72e131a029b85045b68181585d97816a916871ca8d3c208c16d87cfd47"
-      let x = fromHex(BigInt[254], p)
+      let x = BigInt[254].fromHex(p)
       let hex = x.dumpHex(bigEndian)
 
       check: p == hex
 
     block: # BLS12-381 - https://github.com/ethereum/py_ecc/blob/master/py_ecc/fields/field_properties.py
       const p = "0x1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaaab"
-      let x = fromHex(BigInt[381], p)
+      let x = BigInt[381].fromHex(p)
       let hex = x.dumpHex(bigEndian)
 
       check: p == hex