Add CMake support (#121)

Author: lsawade

.gitignore

@@ -14,6 +14,11 @@ doc/gh-pages/
 
 # Test artifacts
 test/testdata-*
+Testing
 
 TODO
 TODO.txt
+
+# CMake directories 
+build
+install

CMAKE.md

@@ -0,0 +1,210 @@
+# Building libmseed with CMake
+
+This document describes how to build and install libmseed using CMake.
+
+## Quick Start
+
+### Building the library
+
+```bash
+# Configure the build
+cmake -B build -S .
+
+# Build the library
+cmake --build build
+
+# Install the library
+cmake --install build
+```
+
+### Using in another CMake project
+
+After installing libmseed, you can use it in your CMake project:
+
+```cmake
+# Find the package
+find_package(libmseed REQUIRED)
+
+# Link against your target
+add_executable(myapp main.c)
+target_link_libraries(myapp PRIVATE mseed::mseed)
+```
+
+## Build Options
+
+The following options can be configured during the CMake configuration step:
+
+| Option | Default | Description |
+|--------|---------|-------------|
+| `BUILD_SHARED_LIBS` | `ON` | Build shared libraries |
+| `BUILD_STATIC_LIBS` | `ON` | Build static libraries |
+| `BUILD_EXAMPLES` | `OFF` | Build example programs |
+| `BUILD_TESTS` | `OFF` | Build test suite |
+| `LIBMSEED_URL` | `OFF` | Enable URL support via libcurl |
+
+### Examples
+
+Build only static library:
+```bash
+cmake -B build -DBUILD_SHARED_LIBS=OFF -DBUILD_STATIC_LIBS=ON
+```
+
+Build with examples and tests:
+```bash
+cmake -B build -DBUILD_EXAMPLES=ON -DBUILD_TESTS=ON
+```
+
+Enable URL support with libcurl:
+```bash
+cmake -B build -DLIBMSEED_URL=ON
+```
+
+Custom installation prefix:
+```bash
+cmake -B build -DCMAKE_INSTALL_PREFIX=/opt/libmseed
+cmake --build build
+cmake --install build
+```
+
+## Installation
+
+The install step will install:
+- Library files (static and/or shared) to `lib/`
+- Header file (`libmseed.h`) to `include/`
+- CMake config files to `lib/cmake/libmseed/`
+- pkg-config file to `lib/pkgconfig/`
+- Documentation files to `share/doc/libmseed/`
+- Example source code to `share/doc/libmseed/examples/`
+
+## Using libmseed in Your Project
+
+### Method 1: CMake find_package (Recommended)
+
+After installing libmseed, you can use it in your CMake project:
+
+```cmake
+cmake_minimum_required(VERSION 3.12)
+project(MyProject)
+
+# Find libmseed
+find_package(libmseed REQUIRED)
+
+# Create your executable
+add_executable(myapp main.c)
+
+# Link against libmseed
+target_link_libraries(myapp PRIVATE mseed::mseed)
+```
+
+If libmseed is installed in a non-standard location:
+```bash
+cmake -B build -DCMAKE_PREFIX_PATH=/opt/libmseed
+```
+
+### Method 2: Using as a subdirectory
+
+You can also include libmseed directly in your project:
+
+```cmake
+cmake_minimum_required(VERSION 3.12)
+project(MyProject)
+
+# Add libmseed as subdirectory
+add_subdirectory(external/libmseed)
+
+# Create your executable
+add_executable(myapp main.c)
+
+# Link against libmseed
+target_link_libraries(myapp PRIVATE mseed::mseed)
+```
+
+### Method 3: pkg-config
+
+If you prefer pkg-config:
+
+```cmake
+find_package(PkgConfig REQUIRED)
+pkg_check_modules(LIBMSEED REQUIRED mseed)
+
+add_executable(myapp main.c)
+target_link_libraries(myapp PRIVATE ${LIBMSEED_LIBRARIES})
+target_include_directories(myapp PRIVATE ${LIBMSEED_INCLUDE_DIRS})
+```
+
+## Running Tests
+
+If you built with tests enabled:
+
+```bash
+cmake -B build -DBUILD_TESTS=ON
+cmake --build build
+cd build
+ctest
+```
+
+## Cross-compilation
+
+CMake makes cross-compilation straightforward. Example for cross-compiling to ARM:
+
+```bash
+cmake -B build -DCMAKE_TOOLCHAIN_FILE=/path/to/arm-toolchain.cmake
+cmake --build build
+```
+
+## Integration with FetchContent
+
+You can also use CMake's FetchContent to automatically download and build libmseed:
+
+```cmake
+include(FetchContent)
+
+FetchContent_Declare(
+    libmseed
+    GIT_REPOSITORY https://github.com/EarthScope/libmseed.git
+    GIT_TAG        v3.1.11
+)
+
+FetchContent_MakeAvailable(libmseed)
+
+add_executable(myapp main.c)
+target_link_libraries(myapp PRIVATE mseed::mseed)
+```
+
+## Troubleshooting
+
+### Library not found
+If CMake cannot find libmseed, ensure it's installed and either:
+1. Set `CMAKE_PREFIX_PATH` to the installation directory
+2. Set `libmseed_DIR` to the directory containing `libmseedConfig.cmake`
+
+Example:
+```bash
+cmake -B build -Dlibmseed_DIR=/usr/local/lib/cmake/libmseed
+```
+
+### URL support issues
+If enabling URL support fails, ensure libcurl is installed:
+```bash
+# Ubuntu/Debian
+sudo apt-get install libcurl4-openssl-dev
+
+# macOS
+brew install curl
+
+# Fedora/RHEL
+sudo dnf install libcurl-devel
+```
+
+## Comparison with Makefile
+
+The CMake build system provides several advantages over the traditional Makefile:
+
+- Better cross-platform support (Windows, macOS, Linux)
+- Easier integration with other CMake projects
+- Automatic dependency detection
+- Support for multiple build systems (Make, Ninja, Visual Studio, Xcode)
+- Better support for IDEs
+- Modern package management (find_package, FetchContent)
+
+Both build systems are maintained and fully supported.