Add support for reading and writing zip files.

.github/scripts/buildzlib.ps1

@@ -0,0 +1,155 @@
+#
+# This source file is part of the Swift.org open source project
+#
+# Copyright (c) 2026 Apple Inc. and the Swift project authors
+# Licensed under Apache License v2.0 with Runtime Library Exception
+#
+# See https://swift.org/LICENSE.txt for license information
+# See https://swift.org/CONTRIBUTORS.txt for Swift project authors
+#
+
+<#
+.SYNOPSIS
+    Fetches a pinned zlib release and builds it as a static library on Windows.
+
+.DESCRIPTION
+    Downloads the source tarball for a specific zlib release then configures
+    and builds with CMake (Visual Studio generator by default, or whatever
+    -Generator specifies). Only the static target is built. Output goes to
+    <OutDir>\include and <OutDir>\lib.
+
+.PARAMETER WorkDir
+    Scratch directory for the download, extracted source and build tree.
+
+.PARAMETER OutDir
+    Where the headers and zlib static library are installed.
+
+.PARAMETER Config
+    Release or Debug.
+
+.PARAMETER Arch
+    Target architecture for the Visual Studio generator: x64, Win32 or ARM64.
+
+.PARAMETER StaticRuntime
+    Link the static MSVC runtime (/MT) instead of the DLL runtime (/MD).
+
+.PARAMETER Generator
+    CMake generator. Defaults to the newest Visual Studio found by CMake.
+
+.PARAMETER Version
+    The zlib release to build, without the leading 'v'. Defaults to 1.3.2.
+
+.EXAMPLE
+    .\buildzlib.ps1 -OutDir C:\libs\zlib -StaticRuntime
+#>
+[CmdletBinding()]
+param(
+    [string]$WorkDir = (Join-Path $PWD 'zlib-build'),
+    [string]$OutDir = (Join-Path $PWD 'zlib-install'),
+    [ValidateSet('Release', 'Debug')][string]$Config = 'Release',
+    [ValidateSet('x64', 'Win32', 'ARM64')][string]$Arch = 'x64',
+    [switch]$StaticRuntime,
+    [string]$Generator,
+    [string]$Version = '1.3.2'
+)
+
+$ErrorActionPreference = 'Stop'
+$ProgressPreference = 'SilentlyContinue'   # Invoke-WebRequest is very slow otherwise
+[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12 -bor [Net.SecurityProtocolType]::Tls13
+
+function Invoke-Native {
+    & $args[0] $args[1..($args.Length - 1)]
+    if ($LASTEXITCODE -ne 0) { throw "'$($args -join ' ')' failed with exit code $LASTEXITCODE" }
+}
+
+foreach ($tool in 'cmake', 'tar') {
+    if (-not (Get-Command $tool -ErrorAction SilentlyContinue)) {
+        throw "Required tool '$tool' not found on PATH. Install CMake and run from a VS Developer prompt if needed."
+    }
+}
+
+# 1. Choose the version
+$zlibVersion = $Version.TrimStart('v')
+Write-Host "zlib version: $zlibVersion"
+
+# 2. Download and extract into fresh directories
+$downloadDir = Join-Path $WorkDir "download-$zlibVersion"
+$srcRoot = Join-Path $WorkDir "src-$zlibVersion"
+$buildDir = Join-Path $WorkDir "build-$zlibVersion-$Arch"
+foreach ($d in $downloadDir, $srcRoot, $buildDir) {
+    if (Test-Path $d) { Remove-Item $d -Recurse -Force }
+    New-Item -ItemType Directory -Path $d | Out-Null
+}
+
+$url = "https://github.com/madler/zlib/releases/download/v$zlibVersion/zlib-$zlibVersion.tar.gz"
+$archive = Join-Path $downloadDir "zlib-$zlibVersion.tar.gz"
+Write-Host "Downloading $url"
+Invoke-WebRequest $url -OutFile $archive
+
+# Paths are passed as arguments; nothing is run from inside the extracted tree.
+Invoke-Native tar -xzf $archive -C $srcRoot
+$srcDir = (Get-ChildItem $srcRoot -Directory | Select-Object -First 1).FullName
+if (-not $srcDir) { throw 'Archive did not extract to a directory.' }
+
+# 3. Configure
+$cmakeArgs = @('-S', $srcDir, '-B', $buildDir)
+if ($Generator) { $cmakeArgs += @('-G', $Generator) }
+if (-not $Generator -or $Generator -like 'Visual Studio*') { $cmakeArgs += @('-A', $Arch) }
+$cmakeArgs += '-DZLIB_BUILD_SHARED=OFF'    # ignored by older releases; we only build zlibstatic anyway
+if ($StaticRuntime) {
+    $cmakeArgs += '-DCMAKE_POLICY_DEFAULT_CMP0091=NEW'
+    $cmakeArgs += '-DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreaded$<$<CONFIG:Debug>:Debug>'
+}
+Invoke-Native cmake @cmakeArgs
+
+# 4. Build only the static library
+Invoke-Native cmake --build $buildDir --config $Config --target zlibstatic --parallel
+
+# 5. Install headers and library
+$incOut = Join-Path $OutDir 'include'
+$libOut = Join-Path $OutDir 'lib'
+New-Item -ItemType Directory -Force -Path $incOut, $libOut | Out-Null
+
+# zconf.h is generated into the build tree; the source copy is renamed zconf.h.included
+Copy-Item (Join-Path $srcDir 'zlib.h') $incOut -Force
+$zconf = Join-Path $buildDir 'zconf.h'
+if (-not (Test-Path $zconf)) { $zconf = Join-Path $srcDir 'zconf.h' }
+Copy-Item $zconf $incOut -Force
+
+# Multi-config generators put the lib under <build>\<Config>; single-config in <build>.
+# Pre-1.3.2, the output is named zlibstatic or, for debug, zlibstaticd.
+# As of zlib-1.3.2, the output is named zs or, for debug, zsd.
+# Normalize to zlib[d]
+$built = Get-ChildItem $buildDir -Recurse -Filter 'z*.lib' |
+    Where-Object { $_.Directory.Name -in $Config, (Split-Path $buildDir -Leaf) } |
+    Select-Object -First 1
+if (-not $built) { $built = Get-ChildItem $buildDir -Recurse -Filter 'z*.lib' | Select-Object -First 1 }
+if (-not $built) { throw 'Could not find the built static library.' }
+
+$destName = $built.Name -replace '^(zlibstatic|zs)', 'zlib'
+Copy-Item $built.FullName (Join-Path $libOut $destName) -Force
+
+# Write a pkgconfig file
+$pcName = Join-Path $OutDir 'zlib.pc'
+
+# pkg-config treats backslash as an escape character, so use forward slashes
+$pcLib = $libOut -replace '\\', '/'
+$pcInc = $incOut -replace '\\', '/'
+# Quote paths containing whitespace, so they stay a single flag argument
+if ($pcLib -match '\s') { $pcLib = "`"$pcLib`"" }
+if ($pcInc -match '\s') { $pcInc = "`"$pcInc`"" }
+$pcLibName = [System.IO.Path]::GetFileNameWithoutExtension($destName)
+
+@"
+Name: zlib
+Version: $zlibVersion
+Description: zlib compression library
+Libs: -L$pcLib -l$pcLibName
+Cflags: -I$pcInc
+"@ | Out-File $pcName -Encoding ascii
+
+Write-Host ''
+Write-Host "zlib $zlibVersion ($Config, $Arch) built successfully."
+Write-Host "  Headers:   $incOut"
+Write-Host "  Library:   $(Join-Path $libOut $destName)"
+Write-Host "  pkgconfig: $pcName"

.github/workflows/pull_request.yml

@@ -24,15 +24,29 @@ jobs:
       # due to issues with filenames on Windows. For now, the Windows CI runs
       # build the package, and only build the tests without running them.
       # Filenames PR: https://github.com/swiftlang/swift-docc/pull/668
-      windows_build_command: "Invoke-Program swift build --build-tests"
+
+      # Windows needs to build a copy of zlib first, because SwiftPM isn't
+      # able to fetch a built copy there.  The CMake build below needs it too,
+      # because nothing else provides ZLIB::ZLIB on Windows.
+      windows_pre_build_command: |
+        Invoke-Program .\.github\scripts\prebuild.ps1 -InstallCMake -SkipAndroid
+        Invoke-Program .\.github\scripts\buildzlib.ps1 -OutDir $Env:TEMP\zlib -WorkDir $Env:TEMP\zlib-build
+      windows_build_command: 'Invoke-Program swift build --pkg-config-path $Env:TEMP\zlib --build-tests'
+
+      # We don't support Swift 6.1 any more
+      macos_exclude_xcode_versions: "[{\"xcode_version\": \"swift_6.1\"}]"
+      linux_exclude_swift_versions: "[{\"swift_version\": \"6.1\"}]"
+      windows_exclude_swift_versions: "[{\"swift_version\": \"6.1\"}]"
 
   cmake:
     name: CMake
     uses: swiftlang/github-workflows/.github/workflows/swift_package_test.yml@0.0.15
     with:
       enable_linux_checks: false
       windows_swift_versions: '["nightly-6.4.x"]'
-      windows_pre_build_command: 'Invoke-Program .\.github\scripts\prebuild.ps1 -InstallCMake -SkipAndroid'
+      windows_pre_build_command: |
+        Invoke-Program .\.github\scripts\prebuild.ps1 -InstallCMake -SkipAndroid
+        Invoke-Program .\.github\scripts\buildzlib.ps1 -OutDir $Env:TEMP\zlib -WorkDir $Env:TEMP\zlib-build
       windows_build_command: |
         $Src = Join-Path $PWD ".build\checkouts"
         $Bin = Join-Path $PWD "BinaryCache"
@@ -61,7 +75,7 @@ jobs:
         Build "$Bin\swift-lmdb" "$Src\swift-lmdb" @("-DBUILD_SHARED_LIBS=NO")
         Build "$Bin\swift-docc-symbolkit" "$Src\swift-docc-symbolkit" @("-DBUILD_SHARED_LIBS=NO")
         # Build DocC
-        Build "$Bin\swift-docc" "$PWD" @("-DBUILD_SHARED_LIBS=YES", "-DArgumentParser_DIR=$Bin\swift-argument-parser\cmake\modules", "-DSwiftASN1_DIR=$Bin\swift-asn1\cmake\modules", "-DSwiftCrypto_DIR=$Bin\swift-crypto\cmake\modules", "-DSwiftMarkdown_DIR=$Bin\swift-markdown\cmake\modules", "-DLMDB_DIR=$Bin\swift-lmdb\cmake\modules", "-DSymbolKit_DIR=$Bin\swift-docc-symbolkit\cmake\modules", "-Dcmark-gfm_DIR=$Install\swift-cmark\lib\cmake")
+        Build "$Bin\swift-docc" "$PWD" @("-DBUILD_SHARED_LIBS=YES", "-DArgumentParser_DIR=$Bin\swift-argument-parser\cmake\modules", "-DSwiftASN1_DIR=$Bin\swift-asn1\cmake\modules", "-DSwiftCrypto_DIR=$Bin\swift-crypto\cmake\modules", "-DSwiftMarkdown_DIR=$Bin\swift-markdown\cmake\modules", "-DLMDB_DIR=$Bin\swift-lmdb\cmake\modules", "-DSymbolKit_DIR=$Bin\swift-docc-symbolkit\cmake\modules", "-DZLIB_ROOT=$Env:TEMP\zlib", "-Dcmark-gfm_DIR=$Install\swift-cmark\lib\cmake")
 
   soundness:
     name: Soundness

.swift-format

@@ -0,0 +1,5 @@
+{
+  "indentation": {
+    "spaces": 4
+  }
+}

CMakeLists.txt

@@ -38,6 +38,7 @@ find_package(SwiftMarkdown)
 find_package(LMDB)
 find_package(SymbolKit)
 find_package(cmark-gfm)
+find_package(ZLIB)
 
 add_compile_options("$<$<COMPILE_LANGUAGE:Swift>:-package-name;SwiftDocC>")
 

Package.swift

@@ -92,6 +92,7 @@ let package = Package(
             dependencies: [
                 .target(name: "DocCCommon"),
                 .target(name: "DocCHTML"),
+                .target(name: "Zip"),
                 .product(name: "Markdown", package: "swift-markdown"),
                 .product(name: "SymbolKit", package: "swift-docc-symbolkit"),
                 .product(name: "CLMDB", package: "swift-lmdb"),
@@ -225,6 +226,36 @@ let package = Package(
             ],
             swiftSettings: swiftSettings(.v5)
         ),
+
+        // Zip file handling
+        .target(
+            name: "Zip",
+            dependencies: [
+                .target(name: "ZLib")
+            ],
+            exclude: ["CMakeLists.txt"],
+            swiftSettings: swiftSettings(.v6)
+        ),
+        .testTarget(
+            name: "ZipTests",
+            dependencies: [
+                .target(name: "Zip")
+            ],
+            swiftSettings: swiftSettings(.v6)
+        ),
+
+        .systemLibrary(
+            name: "CZLib",
+            pkgConfig: "zlib"
+        ),
+        .target(
+            name: "ZLib",
+            dependencies: [
+                .target(name: "CZLib")
+            ],
+            exclude: ["CMakeLists.txt"],
+            swiftSettings: swiftSettings(.v6)
+        )
     ]
 )
 

Sources/CMakeLists.txt

@@ -12,3 +12,5 @@ add_subdirectory(DocCHTML)
 add_subdirectory(SwiftDocC)
 add_subdirectory(DocCCommandLine)
 add_subdirectory(docc)
+add_subdirectory(Zip)
+add_subdirectory(ZLib)

Sources/CZLib/CZLib.h

@@ -0,0 +1,11 @@
+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright (c) 2026 Apple Inc. and the Swift project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See https://swift.org/LICENSE.txt for license information
+ See https://swift.org/CONTRIBUTORS.txt for Swift project authors
+*/
+
+#include <zlib.h>

Sources/CZLib/module.modulemap

@@ -0,0 +1,4 @@
+module CZLib {
+  header "CZLib.h"
+  export *
+}

Sources/SwiftDocC/CMakeLists.txt

@@ -472,12 +472,13 @@ add_library(SwiftDocC
   Utility/SymbolGraphAvailability+Filter.swift
   Utility/Synchronization.swift
   Utility/ValidatedURL.swift
-  Utility/Version.swift)
-target_link_libraries(SwiftDocC PRIVATE
-  DocCCommon)
+  Utility/Version.swift
+  Utility/ZipFileReader+ReadOnlyFileManagerProtocol.swift)
 target_link_libraries(SwiftDocC PRIVATE
+  DocCCommon
   DocCHTML)
 target_link_libraries(SwiftDocC PUBLIC
+  Zip
   SwiftMarkdown::Markdown
   DocC::SymbolKit
   LMDB::CLMDB