First working version

cmd/pkg-config/main.go

@@ -0,0 +1,175 @@
+// cmd/pkg-config is a Go-centric and GOPATH-aware pkg-config replacement
+// for use with the cgo tool.
+//
+// Using cmd/pkg-config with the cgo command
+//
+// To use cmd/pkg-config go install it and ensure it's in the PATH. A NOTE for
+// Linux users: the cmd/pkg-config must be present before original
+// /usr/bin/pkg-config in the PATH list; it is not advised to replace it,
+// as cmd/pkg-config is not a full replacement for the pkg-config tool, e.g.
+// it does not implement conflict and dependency resolving.
+//
+// The cgo tool uses pkg-config for obtaining CFLAGS and LDFLAGS of C libraries.
+// Example:
+//
+//   // #cgo pkg-config: libpng
+//   // #include <png.h>
+//   import "C"
+//
+// The "#cgo pkg-config: png" directive makes a cgo tool query a pkg-config for
+// CFLAGS during generation of a C wrapper (--cflags flag) and for LDFLAGS during
+// linking (--libs flag). The original pkg-config looks up a libpng.pc file in
+// a directory list specified by the PKG_CONFIG_PATH environment variable plus
+// a few other default ones. The libpng.pc file can have the following content:
+//
+//   prefix=/usr
+//   exec_prefix=${prefix}
+//   libdir=${prefix}/lib/x86_64-linux-gnu
+//   includedir=${prefix}/include/libpng12
+//
+//   Name: libpng
+//   Description: Loads and saves PNG files
+//   Version: 1.2.46
+//   Libs: -L${libdir} -lpng12
+//   Libs.private: -lz -lm
+//   Cflags: -I${includedir}
+//
+// A .pc file is composed of two parts - variables and keywords. Keywords may
+// reference pre-declared variables.
+//
+//   $ pkg-config --cflags libpng
+//   -I/usr/include/libpng12
+//   $ pkg-config --libs libpng
+//   -L/usr/lib/x86_64-linux-gnu -lpng12
+//   $ pkg-config --cflags --libs libpng
+//   -I/usr/include/libpng12 -L/usr/lib/x86_64-linux-gnu -lpng12
+//
+// The cmd/pkg-config tool looks up for a PC file in two other places in addition
+// do the original pkg-config: $GOPATH and github.com.
+//
+// The cmd/pkg-config tool and $GOPATH
+//
+// The cmd/pkg-config defines standard directory layout for C libraries:
+//
+//   - $GOPATH/lib contains both the .pc files and binaries
+//   - $GOPATH/include contains package headers
+//
+// The $GOPATH tree for the example may look like the following:
+//
+//   $GOPATH
+//   ├── include
+//   │   └── libpng
+//   │       └── libpng12
+//   │           ├── pngconf.h
+//   │           └── png.h
+//   ├── lib
+//   │   ├── linux_amd64
+//   │   │   └── libpng
+//   │   │       ├── libpng12.so
+//   │   │       └── libpng.pc
+//   │   └── windows_amd64
+//   │       └── libpng
+//   │           ├── libpng12.dll
+//   │           ├── libpng12.dll.a
+//   │           └── libpng.pc
+//   └── src
+//       └── github.com
+//           └── joe
+//               └── png-wrapper
+//                   └── png-wrapper.go
+//
+// The cmd/pkg-config reads the libpng.pc file from $GOPATH/lib/libpng/$GOOS_$GOARCH/libpng.pc.
+// The .pc file written for cmd/pkg-config can use $GOPATH, $GOOS and $GOARCH
+// builtin variables, which are expanded by the cmd/pkg-config during runtime.
+// The rewritten .pc file for libpng may look like the following:
+//
+//   libdir=${GOPATH}/lib/${GOOS}_${GOARCH}/libpng
+//   includedir=${GOPATH}/include/libpng
+//
+//   Name: libpng
+//   Description: Loads and saves PNG files
+//   Version: 1.2.46
+//   Libs: -L${libdir} -lpng12
+//   Libs.private: -lz -lm
+//   Cflags: -I${includedir}
+//
+// The cmd/pkg-config tool and github.com
+//
+// Although it's advised to always use an official or self-compiled libraries for
+// a production use, cmd/pkg-config can download a zip archive from project's
+// github.com releases for a pkg-config tag and unpack it into $GOPATH.
+// For example in order to make the above github.com/joe/png-wrapper package
+// pkg-config-gettable, it's enough to zip include/ and lib/ directories:
+//
+//   $ zip -9 -r libpng.zip include dir
+//
+// Create release, name a tag after pkg-config and attach libpng.zip do the
+// file list. This would make the libpng.zip archive be accessible from the following
+// link:
+//
+//   $ wget http://github.com/joe/png-wrapper/releases/download/pkg-config/libpng.zip
+//
+// Which is the default location the cmd/pkg-config searches for libraries. Then
+// go-getting a joe/png-wrapper package altogether with C dependencies is as
+// easy as:
+//
+//   $ go get github.com/joe/png-wrapper
+//
+// The cmd/pkg-config tool looks up a .pc file for a $LIBRARY in the following order:
+//
+//   - $GOPATH/lib/$GOOS_$GOARCH/$LIBRARY/$LIBRARY.pc
+//   - http://github.com/$USER/$PROJECT/releases/download/pkg-config/$LIBRARY.zip
+//   - $PKG_CONFIG_PATH and eventual pkg-config's default search locations (platform-specific)
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/rjeczalik/pkgconfig"
+)
+
+const USAGE = `NAME:
+		pkg-config - Go-centric pkg-config replacement
+
+USAGE:
+		pkg-config --libs PKG
+		pkg-config --cflags PKG
+		pkg-config --cflags --libs PKG1 PKG2
+		pkg-config get github.com/USER/PROJ PKG`
+
+func die(v ...interface{}) {
+	for _, v := range v {
+		fmt.Fprintln(os.Stderr, v)
+	}
+	os.Exit(1)
+}
+
+func ishelp(s string) bool {
+	return s == "-h" || s == "-help" || s == "help" || s == "--help" || s == "/?"
+}
+
+func main() {
+	if len(os.Args) == 1 || (len(os.Args) == 2 && ishelp(os.Args[1])) {
+		fmt.Println(USAGE)
+	} else {
+		switch os.Args[1] {
+		case "get":
+			if len(os.Args) != 4 {
+				die(USAGE)
+			}
+			pc, err := pkgconfig.LookupGithubProj(os.Args[3], os.Args[2])
+			if err != nil {
+				die(err)
+			}
+			_ = pc
+		default:
+			pkg := pkgconfig.NewPkgArgs(os.Args[1:])
+			if err := pkg.Resolve(); err == nil {
+				pkg.WriteTo(os.Stdout)
+			} else {
+				die(err)
+			}
+		}
+	}
+}

github.go

@@ -0,0 +1,188 @@
+package pkgconfig
+
+import (
+	"archive/zip"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+var githubProj string
+
+func init() {
+	if wd, err := os.Getwd(); err == nil {
+		githubProj = extractproj(wd, os.PathSeparator)
+	}
+}
+
+var src = map[rune]string{'/': "/src/", '\\': `\src\`}
+
+var projpath = map[rune]func(string) string{
+	'/':  func(s string) string { return s },
+	'\\': func(s string) string { return strings.Replace(s, "\\", "/", -1) },
+}
+
+func extractproj(path string, sep rune) (proj string) {
+	n := strings.LastIndex(path, src[sep])
+	if n == -1 {
+		return
+	}
+	n += len(src[sep])
+	m := n
+	for i := 0; i < 3; i++ {
+		l := strings.Index(path[m:], string(sep))
+		if l == -1 {
+			m = len(path) + 1
+			break
+		}
+		m += l + 1
+	}
+	proj = projpath[sep](string(path[n : m-1]))
+	if !strings.HasPrefix(proj, "github.com") {
+		proj = ""
+	}
+	return
+}
+
+// LookupGithub TODO(rjeczalik): document
+func LookupGithub(pkg string) (*PC, error) {
+	if githubProj == "" {
+		return nil, errors.New(`unable to guess project's URL from $CWD`)
+	}
+	return LookupGithubProj(pkg, githubProj)
+}
+
+var targets = map[string]struct{}{
+	"darwin_386":    {},
+	"darwin_amd64":  {},
+	"freebsd_386":   {},
+	"freebsd_amd64": {},
+	"freebsd_arm":   {},
+	"linux_386":     {},
+	"linux_amd64":   {},
+	"linux_arm":     {},
+	"netbsd_386":    {},
+	"netbsd_amd64":  {},
+	"netbsd_arm":    {},
+	"openbsd_386":   {},
+	"openbsd_amd64": {},
+	"plan9_386":     {},
+	"plan9_amd64":   {},
+	"windows_386":   {},
+	"windows_amd64": {},
+}
+
+const targetsMinKeyLen = 9
+
+func validFile(path, pkg string) bool {
+	switch {
+	case strings.HasPrefix(path, "include/"):
+		i := len("include/")
+		if len(path) < i+len(pkg)+1 {
+			return false
+		}
+		n := strings.Index(path[i:], "/")
+		if n == -1 {
+			return false
+		}
+		return string(path[i:i+n]) == pkg
+	case strings.HasPrefix(path, "lib/"):
+		i := len("lib/")
+		if len(path) < i+targetsMinKeyLen+1+len(pkg)+1 {
+			return false
+		}
+		n := strings.Index(path[i:], "/")
+		if n == -1 {
+			return false
+		}
+		if _, ok := targets[string(path[i:i+n])]; !ok {
+			return false
+		}
+		i += n + 1
+		if n = strings.Index(path[i:], "/"); n == -1 {
+			return false
+		}
+		return string(path[i:i+n]) == pkg
+	}
+	return false
+}
+
+var replacefile = map[rune]func(string) string{
+	'/':  func(s string) string { return s },
+	'\\': func(s string) string { return strings.Replace(s, "/", "\\", -1) },
+}
+
+func copyFile(gopath string, f *zip.File) (err error) {
+	rc, err := f.Open()
+	if err != nil {
+		return
+	}
+	defer rc.Close()
+	dir := filepath.Join(gopath, replacefile[os.PathSeparator](path.Dir(f.Name)))
+	if err = os.MkdirAll(dir, 0755); err != nil {
+		return
+	}
+	file, err := os.OpenFile(filepath.Join(dir, path.Base(f.Name)), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
+	if err != nil {
+		return
+	}
+	_, err = io.Copy(file, rc)
+	file.Close()
+	return
+}
+
+// LookupGithunProj TODO(rjeczalik): document
+func LookupGithubProj(pkg, proj string) (*PC, error) {
+	path := os.Getenv("GOPATH")
+	if p := strings.Split(path, string(os.PathListSeparator)); len(path) != 0 {
+		path = p[0]
+	}
+	if path == "" {
+		return nil, errors.New("$GOPATH is empty")
+	}
+	url := fmt.Sprintf("http://%s/releases/download/pkg-config/%s.zip", proj, pkg)
+	res, err := http.Get(url)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	if res.StatusCode == http.StatusNotFound {
+		return nil, errors.New("not found: " + url)
+	}
+	f, err := ioutil.TempFile("", pkg)
+	if err != nil {
+		return nil, err
+	}
+	if _, err = io.Copy(f, res.Body); err != nil {
+		f.Close()
+		os.Remove(f.Name())
+		return nil, err
+	}
+	f.Close()
+	r, err := zip.OpenReader(f.Name())
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		r.Close()
+		os.Remove(f.Name())
+	}()
+	for _, f := range r.File {
+		// Filter out directories.
+		if f.Name[len(f.Name)-1] != '/' {
+			if !validFile(f.Name, pkg) {
+				return nil, fmt.Errorf("unexcpected file %q", f.Name)
+			}
+			if err = copyFile(path, f); err != nil {
+				return nil, err
+			}
+		}
+	}
+	return LookupGopath(pkg)
+}