Add core packages, configuration system, and initial application structure

pkg/encoders/ints/ints.go

@@ -0,0 +1,135 @@
+// Package ints is an optimised encoder for decimal numbers in ASCII format,
+// that simplifies and accelerates encoding and decoding decimal strings. It is
+// faster than strconv in part because it uses a base of 10000 and a lookup
+// table.
+package ints
+
+import (
+	_ "embed"
+	"io"
+
+	"golang.org/x/exp/constraints"
+	"lol.mleku.dev/errorf"
+)
+
+// run this to regenerate (pointlessly) the base 10 array of 4 places per entry
+//go:generate go run ./gen/.
+
+//go:embed base10k.txt
+var base10k []byte
+
+const base = 10000
+
+// T is an integer with a fast codec to decimal ASCII.
+type T struct {
+	N uint64
+}
+
+func New[V constraints.Integer](n V) *T {
+	return &T{uint64(n)}
+}
+
+// Uint64 returns the int.T as a uint64 (the base type)
+func (n *T) Uint64() uint64 { return n.N }
+
+// Int64 returns an int64 from the base number (may cause truncation)
+func (n *T) Int64() int64 { return int64(n.N) }
+
+// Uint16 returns an uint16 from the base number (may cause truncation)
+func (n *T) Uint16() uint16 { return uint16(n.N) }
+
+var powers = []*T{
+	{1},
+	{1_0000},
+	{1_0000_0000},
+	{1_0000_0000_0000},
+	{1_0000_0000_0000_0000},
+}
+
+const zero = '0'
+const nine = '9'
+
+// Marshal the int.T into a byte string.
+func (n *T) Marshal(dst []byte) (b []byte) {
+	nn := n.N
+	b = dst
+	if n.N == 0 {
+		b = append(b, '0')
+		return
+	}
+	var i int
+	var trimmed bool
+	k := len(powers)
+	for k > 0 {
+		k--
+		q := n.N / powers[k].N
+		if !trimmed && q == 0 {
+			continue
+		}
+		offset := q * 4
+		bb := base10k[offset : offset+4]
+		if !trimmed {
+			for i = range bb {
+				if bb[i] != '0' {
+					bb = bb[i:]
+					trimmed = true
+					break
+				}
+			}
+		}
+		b = append(b, bb...)
+		n.N = n.N - q*powers[k].N
+	}
+	n.N = nn
+	return
+}
+
+// Unmarshal reads a string, which must be a positive integer no larger than math.MaxUint64,
+// skipping any non-numeric content before it.
+//
+// Note that leading zeros are not considered valid, but basically no such thing as machine
+// generated JSON integers with leading zeroes. Until this is disproven, this is the fastest way
+// to read a positive json integer, and a leading zero is decoded as a zero, and the remainder
+// returned.
+func (n *T) Unmarshal(b []byte) (r []byte, err error) {
+	if len(b) < 1 {
+		err = errorf.E("zero length number")
+		return
+	}
+	var sLen int
+	if b[0] == zero {
+		r = b[1:]
+		n.N = 0
+		return
+	}
+	// skip non-number characters
+	for i, v := range b {
+		if v >= '0' && v <= '9' {
+			b = b[i:]
+			break
+		}
+	}
+	if len(b) == 0 {
+		err = io.EOF
+		return
+	}
+	// count the digits
+	for ; sLen < len(b) && b[sLen] >= zero && b[sLen] <= nine && b[sLen] != ','; sLen++ {
+	}
+	if sLen == 0 {
+		err = errorf.E("zero length number")
+		return
+	}
+	if sLen > 20 {
+		err = errorf.E("too big number for uint64")
+		return
+	}
+	// the length of the string found
+	r = b[sLen:]
+	b = b[:sLen]
+	for _, ch := range b {
+		ch -= zero
+		n.N = n.N*10 + uint64(ch)
+	}
+	return
+}