example: add program with pre-image oracle usage

.github/workflows/test.yml

@@ -45,7 +45,7 @@ jobs:
             ${{ runner.os }}-go-${{ matrix.go-version }}-
       - name: Build examples
         working-directory: ./example
-        run: make bin/minimal.elf
+        run: make
       - name: build contracts
         working-directory: ./contracts
         run: forge build

example/Makefile

+all: elf dump
+
+.PHONY: elf
+elf: $(patsubst %/go.mod,bin/%.elf,$(wildcard */go.mod))
+
+.PHONY: dump
+dump: $(patsubst %/go.mod,bin/%.dump,$(wildcard */go.mod))
 
 bin:
 	mkdir bin
 
-bin/hello.elf: bin
-	cd hello && GOOS=linux GOARCH=mips GOMIPS=softfloat go build -o ../bin/hello.elf .
-	# verify output with: readelf -h bin/hello.elf
-	# result is mips32, big endian, R3000
+# take any directory with a go mod, and build an ELF
+# verify output with: readelf -h bin/<name>.elf
+# result is mips32, big endian, R3000
+bin/%.elf: bin
+	cd $(@:bin/%.elf=%) && GOOS=linux GOARCH=mips GOMIPS=softfloat go build -o ../$@ .
 
-bin/hello.dump: bin/hello.elf
-	# TODO: currently have the little-endian toolchain, but should use the big-endian one. The -EB compat flag works though.
-	mipsel-linux-gnu-objdump -D --disassembler-options=no-aliases --wide --source -m mips:3000 -EB bin/hello.elf > bin/hello.dump
+# take any ELF and dump it
+# TODO: currently have the little-endian toolchain, but should use the big-endian one. The -EB compat flag works though.
+bin/%.dump: bin/%.elf
+	mipsel-linux-gnu-objdump -D --disassembler-options=no-aliases --wide --source -m mips:3000 -EB $(@:%.dump=%.elf) > $@

example/claim/go.mod

+module claim
+
+go 1.20
+
+require github.com/ethereum-optimism/cannon/preimage v0.0.0
+
+require (
+	golang.org/x/crypto v0.8.0 // indirect
+	golang.org/x/sys v0.7.0 // indirect
+)
+
+replace github.com/ethereum-optimism/cannon/preimage v0.0.0 => ../../preimage

example/claim/go.sum

+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/stretchr/testify v1.8.2 h1:+h33VjcLVPDHtOdpUCuF+7gSuG3yGIftsP1YvFihtJ8=
+golang.org/x/crypto v0.8.0 h1:pd9TJtTueMTVQXzk8E2XESSMQDj/U7OUu0PqJqPXQjQ=
+golang.org/x/crypto v0.8.0/go.mod h1:mRqEX+O9/h5TFCrQhkgjo2yKi0yYA+9ecGkdQoHrywE=
+golang.org/x/sys v0.7.0 h1:3jlCCIQZPdOYu1h8BkNvLz8Kgwtae2cagcG/VamtZRU=
+golang.org/x/sys v0.7.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

example/claim/main.go

+package main
+
+import (
+	"encoding/binary"
+	"fmt"
+	"os"
+
+	"github.com/ethereum-optimism/cannon/preimage"
+)
+
+type rawHint string
+
+func (rh rawHint) Hint() string {
+	return string(rh)
+}
+
+func main() {
+	_, _ = os.Stdout.Write([]byte("started!"))
+
+	po := preimage.NewOracleClient(preimage.ClientPreimageChannel())
+	hinter := preimage.NewHintWriter(preimage.ClientHinterChannel())
+
+	preHash := po.Get(preimage.LocalIndexKey(0))
+	diffHash := po.Get(preimage.LocalIndexKey(1))
+	claimData := po.Get(preimage.LocalIndexKey(2))
+
+	// Hints are used to indicate which things the program will access,
+	// so the server can be prepared to serve the corresponding pre-images.
+	hinter.Hint(rawHint(fmt.Sprintf("fetch-state %x", preHash)))
+	pre := po.Get(preimage.Keccak256Key(preHash))
+
+	// Multiple pre-images may be fetched based on a hint.
+	// E.g. when we need all values of a merkle-tree.
+	hinter.Hint(rawHint(fmt.Sprintf("fetch-diff %x", diffHash)))
+	diff := po.Get(preimage.Keccak256Key(diffHash))
+	diffPartA := po.Get(preimage.Keccak256Key(*(*[32]byte)(diff[:32])))
+	diffPartB := po.Get(preimage.Keccak256Key(*(*[32]byte)(diff[32:])))
+
+	// Example state-transition function: s' = s*a + b
+	s := binary.BigEndian.Uint64(pre)
+	a := binary.BigEndian.Uint64(diffPartA)
+	b := binary.BigEndian.Uint64(diffPartB)
+	fmt.Printf("computing %d * %d + %d\n", s, a, b)
+	sOut := s*a + b
+
+	sClaim := binary.BigEndian.Uint64(claimData)
+	if sOut != sClaim {
+		fmt.Printf("claim %d is bad! Correct result is %d\n", sOut, sClaim)
+		os.Exit(1)
+	} else {
+		fmt.Printf("claim %d is good!\n", sOut)
+		os.Exit(0)
+	}
+}