cmd/packserver: add --immutable flag

Now inherits from --expiry, but with a maximum of 60s. Intended to allow for
short negative caching, without causing issues with newly-created assets.

cmd/packserver/go.mod

@@ -1,15 +1,15 @@
 module src.lwithers.me.uk/go/htpack/cmd/packserver
 
-go 1.22
+go 1.26.0
 
 require (
-	github.com/spf13/cobra v1.8.1
-	src.lwithers.me.uk/go/htpack v1.3.3
+	github.com/spf13/cobra v1.10.2
+	src.lwithers.me.uk/go/htpack v1.5.0
 )
 
 require (
-	github.com/gogo/protobuf v1.3.2 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
-	github.com/spf13/pflag v1.0.5 // indirect
-	golang.org/x/sys v0.22.0 // indirect
+	github.com/spf13/pflag v1.0.10 // indirect
+	golang.org/x/sys v0.47.0 // indirect
+	google.golang.org/protobuf v1.36.12 // indirect
 )

cmd/packserver/go.sum

@@ -1,45 +1,19 @@
-github.com/cpuguy83/go-md2man/v2 v2.0.4/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
-github.com/gogo/protobuf v1.3.2 h1:Ov1cvc58UF3b5XjBnZv7+opcTcQFZebYjWzi34vdm4Q=
-github.com/gogo/protobuf v1.3.2/go.mod h1:P1XiOD3dCwIKUDQYPy72D8LYyHL2YPYrpS2s69NZV8Q=
+github.com/cpuguy83/go-md2man/v2 v2.0.6/go.mod h1:oOW0eioCTA6cOiMLiUPZOpcVxMig6NIQQ7OS05n1F4g=
+github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
+github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
 github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
-github.com/kisielk/errcheck v1.5.0/go.mod h1:pFxgyoBC7bSaBwPgfKdkLd5X25qrDl4LWUI2bnpBCr8=
-github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
-github.com/spf13/cobra v1.8.1 h1:e5/vxKd/rZsfSJMUX1agtjeTDf+qv1/JdBF8gg5k9ZM=
-github.com/spf13/cobra v1.8.1/go.mod h1:wHxEcudfqmLYa8iTfL+OuZPbBZkmvliBWKIezN3kD9Y=
-github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
-github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
-github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
-github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
-golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
-golang.org/x/mod v0.2.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
-golang.org/x/mod v0.3.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
-golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20200226121028-0de0cce0169b/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20201021035429-f5854403a974/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
-golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.22.0 h1:RI27ohtqKCnwULzJLqkv897zojh5/DwS/ENaMzUOaWI=
-golang.org/x/sys v0.22.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
-golang.org/x/tools v0.0.0-20200619180055-7c47624df98f/go.mod h1:EkVYQZoAsY45+roYkvgYkIh4xh/qjgUK9TdY2XT94GE=
-golang.org/x/tools v0.0.0-20210106214847-113979e3529a/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
-golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+github.com/spf13/cobra v1.10.2 h1:DMTTonx5m65Ic0GOoRY2c16WCbHxOOw6xxezuLaBpcU=
+github.com/spf13/cobra v1.10.2/go.mod h1:7C1pvHqHw5A4vrJfjNwvOdzYu0Gml16OCs2GRiTUUS4=
+github.com/spf13/pflag v1.0.9/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/spf13/pflag v1.0.10 h1:4EBh2KAYBwaONj6b2Ye1GiHfwjqyROoF4RwYO+vPwFk=
+github.com/spf13/pflag v1.0.10/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=
+golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=
+golang.org/x/sys v0.47.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
+google.golang.org/protobuf v1.36.12 h1:pJOKDDOyeXErUroCihFAd5LQuwXBSpVnKGrj5o/fwxc=
+google.golang.org/protobuf v1.36.12/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-src.lwithers.me.uk/go/htpack v1.3.3 h1:Xvl6qR9HfSblmCgPyu+ACQ9o3aLQSIy3l8CrMbzj/jc=
-src.lwithers.me.uk/go/htpack v1.3.3/go.mod h1:qKgCBgZ6iiiuYOxZkYOPVpXLBzp6gXEd4A0ksxgR6Nk=
+src.lwithers.me.uk/go/htpack v1.5.0 h1:2UYM4AGIPc/XgktmO6AxUyqFxzmYkqg/jINcDCsZsCk=
+src.lwithers.me.uk/go/htpack v1.5.0/go.mod h1:5dQlPdwV+ZeBAaFBdwiRI6/w5dpSgPsiotO4ZTYau88=

cmd/packserver/main.go

@@ -55,6 +55,10 @@ func main() {
 		"Name of index file (index.html or similar)")
 	rootCmd.Flags().Duration("expiry", 0,
 		"Tell client how long it can cache data for; 0 means no caching")
+	rootCmd.Flags().Duration("expiry404", 0,
+		"Tell client how long it can cache 404 responses for; 0 means default (inherit from --expiry, max. 60s); -1 means no caching")
+	rootCmd.Flags().Bool("immutable", false,
+		"Tell client that cached assets are immutable (will not be revalidated on page reload)")
 	rootCmd.Flags().String("fallback-404", "",
 		"Name of file to return if response would be 404 (spa.html or similar)")
 	rootCmd.Flags().String("frames", "sameorigin",
@@ -135,15 +139,35 @@ func run(c *cobra.Command, args []string) error {
 
 	// parse expiry time
 	//  NB: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control
+	cacheControl200, cacheControl404 := "no-cache", "no-cache"
+	immutable, err := c.Flags().GetBool("immutable")
+	if err != nil {
+		return err
+	}
+	var immutableDirective string
+	if immutable {
+		immutableDirective = ", immutable"
+	}
+
 	expiry, err := c.Flags().GetDuration("expiry")
 	if err != nil {
 		return err
 	}
-	if expiry <= 0 {
-		extraHeaders.Set("Cache-Control", "no-cache")
-	} else {
-		extraHeaders.Set("Cache-Control",
-			fmt.Sprintf("public, max-age=%d", expiry/1e9))
+	if expiry > 0 {
+		cacheControl200 = fmt.Sprintf("public, max-age=%d%s", expiry/1e9, immutableDirective)
+	}
+
+	expiry404, err := c.Flags().GetDuration("expiry404")
+	if err != nil {
+		return err
+	}
+	switch {
+	case expiry404 == 0 && expiry == 0:
+	case expiry404 == 0 && expiry > 0:
+		expiry404 = min(60*time.Second, expiry)
+		fallthrough
+	case expiry404 > 0:
+		cacheControl404 = fmt.Sprintf("public, max-age=%d", expiry404/1e9)
 	}
 
 	// optional index file
@@ -199,6 +223,7 @@ func run(c *cobra.Command, args []string) error {
 		if err != nil {
 			return err
 		}
+		packHandler.SetCacheControl(cacheControl200, cacheControl404)
 		if indexFile != "" {
 			packHandler.SetIndex(indexFile)
 		}

go.mod

@@ -1,8 +1,8 @@
 module src.lwithers.me.uk/go/htpack
 
-require (
-	github.com/gogo/protobuf v1.3.2
-	golang.org/x/sys v0.22.0
-)
+go 1.26.0
 
-go 1.22
+require (
+	golang.org/x/sys v0.47.0
+	google.golang.org/protobuf v1.36.12
+)

go.sum

@@ -1,33 +1,6 @@
-github.com/gogo/protobuf v1.3.2 h1:Ov1cvc58UF3b5XjBnZv7+opcTcQFZebYjWzi34vdm4Q=
-github.com/gogo/protobuf v1.3.2/go.mod h1:P1XiOD3dCwIKUDQYPy72D8LYyHL2YPYrpS2s69NZV8Q=
-github.com/kisielk/errcheck v1.5.0/go.mod h1:pFxgyoBC7bSaBwPgfKdkLd5X25qrDl4LWUI2bnpBCr8=
-github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
-github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
-github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
-golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
-golang.org/x/mod v0.2.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
-golang.org/x/mod v0.3.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
-golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20200226121028-0de0cce0169b/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20201021035429-f5854403a974/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
-golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.22.0 h1:RI27ohtqKCnwULzJLqkv897zojh5/DwS/ENaMzUOaWI=
-golang.org/x/sys v0.22.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
-golang.org/x/tools v0.0.0-20200619180055-7c47624df98f/go.mod h1:EkVYQZoAsY45+roYkvgYkIh4xh/qjgUK9TdY2XT94GE=
-golang.org/x/tools v0.0.0-20210106214847-113979e3529a/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
-golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
+github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
+golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=
+golang.org/x/sys v0.47.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
+google.golang.org/protobuf v1.36.12 h1:pJOKDDOyeXErUroCihFAd5LQuwXBSpVnKGrj5o/fwxc=
+google.golang.org/protobuf v1.36.12/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=

handler.go

@@ -3,14 +3,12 @@ package htpack
 import (
 	"fmt"
 	"net/http"
-	"os"
 	"path"
 	"path/filepath"
 	"strconv"
 	"strings"
 	"time"
 
-	"golang.org/x/sys/unix"
 	"src.lwithers.me.uk/go/htpack/packed"
 )
 
@@ -21,33 +19,18 @@ const (
 
 // New returns a new handler. Standard security headers are set.
 func New(packfile string) (*Handler, error) {
-	f, err := os.Open(packfile)
+	mapped, err := packed.MapAndLoad(packfile)
 	if err != nil {
 		return nil, err
 	}
-	defer f.Close()
-
-	fi, err := f.Stat()
-	if err != nil {
-		return nil, err
-	}
-	mapped, err := unix.Mmap(int(f.Fd()), 0, int(fi.Size()),
-		unix.PROT_READ, unix.MAP_SHARED)
-	if err != nil {
-		return nil, err
-	}
-
-	_, dir, err := packed.Load(f)
-	if err != nil {
-		unix.Munmap(mapped)
-		return nil, err
-	}
 
 	h := &Handler{
-		mapped:    mapped,
-		dir:       dir.Files,
-		headers:   make(map[string]string),
-		startTime: time.Now(),
+		mapped:          mapped.Data,
+		dir:             mapped.Directory.Files,
+		headers:         make(map[string]string),
+		cacheControl200: "no-cache",
+		cacheControl404: "no-cache",
+		startTime:       time.Now(),
 	}
 
 	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Frame-Options
@@ -61,11 +44,13 @@ func New(packfile string) (*Handler, error) {
 
 // Handler implements http.Handler and allows options to be set.
 type Handler struct {
-	mapped    []byte
-	dir       map[string]*packed.File
-	headers   map[string]string
-	startTime time.Time
-	notFound  *packed.File
+	mapped          []byte
+	dir             map[string]*packed.File
+	headers         map[string]string
+	cacheControl200 string
+	cacheControl404 string
+	startTime       time.Time
+	notFound        *packed.File
 }
 
 // SetHeader allows a custom header to be set on HTTP responses. These are
@@ -126,6 +111,19 @@ func (h *Handler) SetNotFound(notFound string) error {
 	return nil
 }
 
+// SetCacheControl allows control over the cache-control header. If not called,
+// "Cache-Control: no-cache" is the default.
+//
+// The first and second arguments are required, and specify the header to use
+// for 200 responses and 404 responses respectively.
+//
+// TODO: could be expanded to take extra varargs for more specific control over
+// particular assets, like different expiry per content-type.
+func (h *Handler) SetCacheControl(hdr200, hdr404 string) {
+	h.cacheControl200 = hdr200
+	h.cacheControl404 = hdr404
+}
+
 // ServeHTTP handles requests for files. It supports GET and HEAD methods, with
 // anything else returning a 405. Exact path matches are required, else a 404 is
 // returned.
@@ -146,6 +144,7 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 
 	info := h.dir[path.Clean(req.URL.Path)]
 	if info == nil {
+		w.Header().Set("Cache-Control", h.cacheControl404)
 		if h.notFound == nil {
 			http.NotFound(w, req)
 			return
@@ -154,6 +153,7 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	}
 
 	// set standard headers
+	w.Header().Set("Cache-Control", h.cacheControl200)
 	w.Header().Set("Vary", "Accept-Encoding")
 	w.Header().Set("Etag", info.Etag)
 	w.Header().Set("Content-Type", info.ContentType)

packed/load.go

@@ -2,9 +2,13 @@ package packed
 
 import (
 	fmt "fmt"
+	"io/fs"
 	"os"
 	"path"
 	"strings"
+
+	"golang.org/x/sys/unix"
+	"google.golang.org/protobuf/proto"
 )
 
 const (
@@ -17,14 +21,14 @@ const (
 	VersionInitial = 1
 )
 
-// Load a ready-packed file.
-func Load(f *os.File) (*Header, *Directory, error) {
-	hdr, err := loadHeader(f)
+// Read a ready-packed file.
+func Read(f []byte) (*Header, *Directory, error) {
+	hdr, err := readHeader(f)
 	if err != nil {
 		return nil, nil, err
 	}
 
-	dir, err := loadDirectory(f, hdr)
+	dir, err := readDirectory(f, hdr)
 	if le, ok := err.(*LoadError); ok {
 		// augment error
 		le.Magic = hdr.Magic
@@ -33,20 +37,101 @@ func Load(f *os.File) (*Header, *Directory, error) {
 	return hdr, dir, err // we may have a partial dir
 }
 
-// loadHeader retrieves and decodes the header from the start of the file. It
-// ensures the magic number and the version number match. Errors are returned
-// as type LoadError.
-func loadHeader(f *os.File) (*Header, error) {
-	raw := make([]byte, 36)
-	if _, err := f.ReadAt(raw, 0); err != nil {
-		return nil, &LoadError{
-			Cause:      IOError,
-			Underlying: err,
+// Mapped holds an mmap()ed packfile.
+type Mapped struct {
+	Data      []byte
+	Header    *Header
+	Directory *Directory
+}
+
+func (m *Mapped) Close() error {
+	return unix.Munmap(m.Data)
+}
+
+// MapAndLoad mmaps the named file and reads the pack data.
+func MapAndLoad(fname string) (*Mapped, error) {
+	f, err := os.Open(fname)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	st, err := f.Stat()
+	if err != nil {
+		return nil, &fs.PathError{
+			Path: fname,
+			Op:   "stat",
+			Err:  err,
 		}
 	}
 
+	data, err := unix.Mmap(int(f.Fd()), 0, int(st.Size()), unix.PROT_READ, unix.MAP_SHARED)
+	if err != nil {
+		return nil, &fs.PathError{
+			Path: fname,
+			Op:   "mmap",
+			Err:  err,
+		}
+	}
+
+	hdr, dir, err := Read(data)
+	if err != nil {
+		unix.Munmap(data)
+		return nil, err
+	}
+
+	return &Mapped{
+		Data:      data,
+		Header:    hdr,
+		Directory: dir,
+	}, nil
+}
+
+// Load a ready-packed file.
+//
+// Deprecated: use [Read] or [MapAndLoad].
+func Load(f *os.File) (*Header, *Directory, error) {
+	// we need to know the size of the file in order to mmap it
+	st, err := f.Stat()
+	if err != nil {
+		return nil, nil, &fs.PathError{
+			Path: f.Name(),
+			Op:   "stat",
+			Err:  err,
+		}
+	}
+
+	// compatibility: old code may have worked with non-zero offset
+	offset, err := f.Seek(0, os.SEEK_CUR)
+	if err != nil {
+		return nil, nil, &fs.PathError{
+			Path: f.Name(),
+			Op:   "seek",
+			Err:  err,
+		}
+	}
+
+	// mmap the file
+	data, err := unix.Mmap(int(f.Fd()), 0, int(st.Size()), unix.PROT_READ, unix.MAP_SHARED)
+	if err != nil {
+		return nil, nil, &fs.PathError{
+			Path: f.Name(),
+			Op:   "mmap",
+			Err:  err,
+		}
+	}
+	defer unix.Munmap(data)
+
+	// read as though it's from memory
+	return Read(data[offset:])
+}
+
+// readHeader retrieves and decodes the header from the start of the file. It
+// ensures the magic number and the version number match. Errors are returned
+// as type LoadError.
+func readHeader(f []byte) (*Header, error) {
 	hdr := new(Header)
-	if err := hdr.Unmarshal(raw); err != nil {
+	if err := proto.Unmarshal(f[:36], hdr); err != nil {
 		return nil, &LoadError{
 			Cause:      HeaderUnmarshalError,
 			Underlying: err,
@@ -77,35 +162,22 @@ func loadHeader(f *os.File) (*Header, error) {
 	return hdr, nil
 }
 
-// loadDirectory reads the directory from a file. The directory is checked
+// readDirectory reads the directory from a file. The directory is checked
 // for consistency (offsets, filenames) but not integrity (file data is not
 // read/checksummed).
-func loadDirectory(f *os.File, hdr *Header) (*Directory, error) {
-	fi, err := f.Stat()
-	if err != nil {
-		return nil, &LoadError{
-			Cause:      IOError,
-			Underlying: err,
-		}
-	}
-	fileSize := uint64(fi.Size())
+func readDirectory(f []byte, hdr *Header) (*Directory, error) {
+	fileSize := uint64(len(f))
+	start := hdr.DirectoryOffset
+	end := start + hdr.DirectoryLength
 
-	if hdr.DirectoryOffset+hdr.DirectoryLength > fileSize {
+	if end > fileSize {
 		return nil, &LoadError{
 			Cause: BadOffsetError,
 		}
 	}
 
-	raw := make([]byte, hdr.DirectoryLength)
-	if _, err := f.ReadAt(raw, int64(hdr.DirectoryOffset)); err != nil {
-		return nil, &LoadError{
-			Cause:      IOError,
-			Underlying: err,
-		}
-	}
-
 	dir := new(Directory)
-	if err := dir.Unmarshal(raw); err != nil {
+	if err := proto.Unmarshal(f[start:end], dir); err != nil {
 		return nil, &LoadError{
 			Cause:      DirectoryUnmarshalError,
 			Underlying: err,

packed/load_test.go

@@ -0,0 +1,39 @@
+package packed
+
+import (
+	"bytes"
+	"os"
+	"testing"
+)
+
+func TestMapAndLoad(t *testing.T) {
+	rawPack, err := os.ReadFile("testdata/helloworld.pack")
+	if err != nil {
+		t.Fatal(err)
+	}
+	rawText, err := os.ReadFile("testdata/helloworld.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	mapped, err := MapAndLoad("testdata/helloworld.pack")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer mapped.Close()
+
+	if !bytes.Equal(mapped.Data, rawPack) {
+		t.Error("mapped data does not match raw file")
+	}
+
+	file := mapped.Directory.Files["/helloworld.txt"]
+	if file == nil {
+		t.Fatal("directory does not contain /helloworld.txt")
+	}
+
+	start := file.Uncompressed.Offset
+	end := start + file.Uncompressed.Length
+	if !bytes.Equal(rawText, mapped.Data[start:end]) {
+		t.Error("uncompressed file does not match testdata/helloworld.txt")
+	}
+}

packed/packed.proto

@@ -1,6 +1,7 @@
 syntax = "proto3";
 
-package packed;
+package lwithers.htpack.packed;
+option go_package = "src.lwithers.me.uk/htpack/packed";
 
 // Header at start of file. This must be a fixed, known size. Fields cannot
 // be zero.
@@ -54,6 +55,6 @@ message FileData {
 	// the pack.
 	fixed64 offset = 1;
 
-	// Length is the 
+	// Length of the (possibly compressed) file data, in bytes.
 	fixed64 length = 2;
 }

packed/testdata/helloworld.txt

@@ -0,0 +1,13 @@
+Hello, world
+
+This file contains a few lines of plain text, really just enough
+to trigger the "compression worthwhile" heuristic.
+
+This file contains a few lines of plain text, really just enough
+to trigger the "compression worthwhile" heuristic.
+
+This file contains a few lines of plain text, really just enough
+to trigger the "compression worthwhile" heuristic.
+
+This file contains a few lines of plain text, really just enough
+to trigger the "compression worthwhile" heuristic.