tdo

commit 290e6e438afe5f422392452da03129afa2eae724
Author: david cochran <about.trout@gmail.com>
Date:   Mon, 31 Jan 2022 02:45:58 +0000

add layer0 solution

Diffstat:
A
README.md
 | 
1
+
A
cmd/layer0/decode.go
 | 
19
+++++++++++++++++++
A
go.mod
 | 
3
+++
A
go.sum
 | 
0

A
input.go
 | 
43
+++++++++++++++++++++++++++++++++++++++++++

5 files changed, 66 insertions(+), 0 deletions(-)
diff --git a/README.md b/README.md
@@ -0,0 +1 @@
+My [Tom's Data Onion](https://www.tomdalling.com/toms-data-onion/) solutions.
diff --git a/cmd/layer0/decode.go b/cmd/layer0/decode.go
@@ -0,0 +1,19 @@
+package main
+
+import (
+	"log"
+	"os"
+
+	"github.com/abtrout/tdo"
+)
+
+func main() {
+	bs, err := tdo.DecodePipedInput()
+	if err != nil {
+		log.Fatalf("Failed to read layer input: %v\n", err)
+	}
+	// DecodePipedInput already ASCII85 decodes; no additional work to do.
+	if _, err := os.Stdout.Write(bs); err != nil {
+		log.Fatalf("Failed to write decoded output: %v\n", err)
+	}
+}
diff --git a/go.mod b/go.mod
@@ -0,0 +1,3 @@
+module github.com/abtrout/tdo
+
+go 1.24.0
diff --git a/go.sum b/go.sum
diff --git a/input.go b/input.go
@@ -0,0 +1,43 @@
+package tdo
+
+import (
+	"bytes"
+	"encoding/ascii85"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+)
+
+// Read piped input from stdin and ascii85 decode.
+func DecodePipedInput() ([]byte, error) {
+	stat, err := os.Stdin.Stat()
+	if err != nil {
+		return nil, err
+	}
+	if (stat.Mode() & os.ModeCharDevice) != 0 {
+		return nil, errors.New("no piped input")
+	}
+	in, err := io.ReadAll(os.Stdin)
+	if err != nil {
+		return nil, err
+	}
+	return decode(in)
+}
+
+// decode is a convenience wrapper around encoding/ascii85, adding
+// support for Adobe version, which the TDO layer inputs use, and
+// enables easy decoding from layer inputs without extra parsing.
+//
+// https://en.wikipedia.org/wiki/Ascii85#Adobe_version
+func decode(bs []byte) ([]byte, error) {
+	_, bs, _ = bytes.Cut(bs, []byte("<~"))
+	bs, _, _ = bytes.Cut(bs, []byte("~>"))
+
+	res := make([]byte, 4*len(bs))
+	ndst, _, err := ascii85.Decode(res, bs, true)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode buffer: %v", err)
+	}
+	return res[:ndst], nil
+}