Initial commit

Author: msmolens

Diff for: .gitignore

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+build/

Diff for: Dockerfile

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+# Dockerfile to build sine and libsndfile for Amazon Linux 2.
+#
+# To build:
+#   docker build -t sine .
+#
+# To copy the binaries to the host system, run:
+#   docker create --name sine-build sine:latest
+#   docker cp sine-build:/usr/local/lib64/libsndfile.so.1.0.29 .
+#   docker cp sine-build:/usr/local/lib64/libsndfile.so.1 .
+#   docker cp sine-build:/usr/local/lib64/libsndfile.so .
+#   docker cp sine-build:/opt/sine/insta//bin/sine .
+#   docker rm sine-build
+#
+
+FROM amazonlinux:2.0.20200406.0
+
+RUN \
+  yum -q -y groupinstall "Development Tools"
+
+RUN \
+  yum -q -y install \
+    cmake3 \
+    ninja-build \
+  && ln -s /usr/bin/cmake3 /usr/bin/cmake
+
+# Build and install libsndfile. Compile as a shared library to conform to LGPL.
+#
+# libsndfile-devel 1.0.25 is available through the package manager, but that
+# version doesn't provide a CMake package configuration file. Therefore, build a
+# more recent version.
+# TODO: Update when https://github.com/erikd/libsndfile/pull/524 is merged.
+ENV LIBSNDFILE_GIT_REF c103c16c972c3c30197ef0da963802ce7c33ad72
+ENV LIBSNDFILE_TARBALL_SHA256 17a43830e869987ae2dca7839363f7317b6ce00dfe161d507ef0b73ccc6b4c42
+WORKDIR /opt/libsndfile
+RUN \
+  curl -L https://api.github.com/repos/msmolens/libsndfile/tarball/${LIBSNDFILE_GIT_REF} > libsndfile.tar.gz && \
+  echo "$LIBSNDFILE_TARBALL_SHA256 libsndfile.tar.gz" | sha256sum -c -w --status - && \
+  mkdir libsndfile && \
+  tar zxf libsndfile.tar.gz --strip-components=1 && \
+  mkdir build && \
+  cd build && \
+  cmake -G Ninja \
+    -DCMAKE_BUILD_TYPE:STRING=Release \
+    -DBUILD_SHARED_LIBS:BOOL=ON \
+    -DBUILD_PROGRAMS:BOOL=OFF \
+    -DBUILD_TESTING:BOOL=OFF \
+    -DENABLE_EXTERNAL_LIBS:BOOL=OFF \
+    .. && \
+  cmake --build . --target install
+
+# Build and install the example sine program.
+ENV INSTALL_PREFIX /opt/sine/install
+WORKDIR /opt/sine/build
+COPY sine .
+RUN mkdir build && \
+  cd build && \
+  cmake -G Ninja \
+    -DCMAKE_BUILD_TYPE=Release \
+    -DCMAKE_INSTALL_PREFIX=${INSTALL_PREFIX} \
+    .. && \
+  cmake --build . --target install && \
+  echo "Shared libraries:" && \
+  ldd ${INSTALL_PREFIX}/bin/sine && \
+  strip ${INSTALL_PREFIX}/bin/sine

Diff for: LICENSE

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+MIT License
+
+Copyright (c) 2020 Max Smolens
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

Diff for: Makefile

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+# Makefile to build sine and libsndfile for Amazon Linux 2.
+
+IMAGE = sine
+NAME = sine-build
+OUTDIR = ./build
+
+.PHONY: all
+
+all: copy
+
+build: Dockerfile
+	docker build -t $(IMAGE) -f Dockerfile .
+
+copy: build
+	mkdir -p $(OUTDIR)
+	docker create --name $(NAME) $(IMAGE)
+	docker cp $(NAME):/usr/local/lib64/libsndfile.so.1.0.29 $(OUTDIR)
+	docker cp $(NAME):/usr/local/lib64/libsndfile.so.1 $(OUTDIR)
+	docker cp $(NAME):/usr/local/lib64/libsndfile.so $(OUTDIR)
+	docker cp $(NAME):/opt/sine/install/bin/sine $(OUTDIR)
+	docker rm $(NAME)
+
+clean:
+	rm -rf $(OUTDIR)
+	docker rm $(NAME) || true
+	docker rmi $(IMAGE) || true

Diff for: README.md

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+# Compile for AWS Lambda
+
+## Overview
+
+For a native executable to run in an AWS Lambda function, it must be compatible
+with the runtime's operating system. This repository is an example of using
+Docker to build a custom C++ executable that runs on AWS Lambda.
+
+## Requirements
+
+- [Docker](https://docs.docker.com/)
+- [Make](https://www.gnu.org/software/make/)
+
+## Usage
+
+Enter this directory and run `make`:
+
+```console
+$ cd /path/to/compile-for-aws-lambda
+$ make
+```
+
+The `build` directory now contains binaries that can be packaged in the ZIP file
+for an AWS Lambda function:
+
+```
+$ tree build
+build
+├── libsndfile.so -> libsndfile.so.1
+├── libsndfile.so.1 -> libsndfile.so.1.0.29
+├── libsndfile.so.1.0.29
+└── sine
+```
+
+The example `sine` program generates a sine wave at the specified frequency (Hz)
+and writes it as a WAV file:
+```console
+$ cd build
+$ export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:.
+$ ./sine 2600 /tmp/2600.wav
+$ file /tmp/2600.wav
+2600.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 24 bit, mono 44100 Hz
+```
+
+To run the program in a Lambda function, use the
+[child_process](https://nodejs.org/docs/latest-v12.x/api/child_process.html)
+module in Node.js, or the
+[subprocess](https://docs.python.org/3.8/library/subprocess.html) module in
+Python.
+
+## Details
+
+From the [Running Arbitrary Executables in AWS
+Lambda](https://aws.amazon.com/blogs/compute/running-executables-in-aws-lambda/)
+blog post:
+
+> If you compile your own binaries, ensure that they’re either statically linked
+> or built for the matching version of Amazon Linux.
+
+The example `sine` program in this repository uses the LGPL-licensed
+[libsndfile](https://github.com/erikd/libsndfile) library. To comply with the
+LPGL, libsndfile must be used as a shared library; it cannot be statically
+linked.
+
+### Dockerfile
+
+To compile binaries that are compatible with Amazon Linux 2, the
+[`Dockerfile`](./Dockerfile) starts from an Amazon Linux 2 base image:
+
+```docker
+FROM amazonlinux:2.0.20200406.0
+```
+
+The Dockerfile then builds and installs `libsndfile` and `sine`. 
+
+Binaries compiled in this environment will run on any AWS Lambda runtime that's
+based on Amazon Linux 2, such as the Node.js 12 and Python 3.8 runtimes. See
+[AWS Lambda
+runtimes](https://docs.aws.amazon.com/lambda/latest/dg/lambda-runtimes.html) for
+a complete list.
+
+### Makefile
+
+The [`Makefile`](./Makefile) creates a container from the Docker image and
+copies the built artifacts from the container to the host system.

Diff for: sine/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.8)
+
+project(sine LANGUAGES CXX)
+
+find_package(SndFile REQUIRED)
+
+add_subdirectory(src)
+add_subdirectory(app)

Diff for: sine/app/CMakeLists.txt

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+add_executable(sine sine.cpp)
+
+target_link_libraries(sine PRIVATE libsine)
+
+install(TARGETS sine
+        RUNTIME DESTINATION bin)

Diff for: sine/app/sine.cpp

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+#include <libsine/libsine.h>
+
+#include <cstdlib>
+#include <iostream>
+#include <string>
+
+int main(int argc, char * argv[]) {
+    if (argc != 3) {
+        std::cerr << "USAGE: " << argv[0] << " <frequency (Hz)> <filename>" << std::endl;
+        return 1;
+    }
+
+    // Parse arguments
+    float frequency = atof(argv[1]);
+    std::string filename(argv[2]);
+
+    // Generate WAV file
+    auto result = sine::generate_sine(frequency, filename);
+
+    return result ? 0 : 1;
+}

Diff for: sine/include/libsine/libsine.h

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+#ifndef LIBSINE_H
+#define LIBSINE_H
+
+#include <string>
+
+namespace sine
+{
+
+// Generate a mono WAV file of a sine function at the specified frequency.
+// Returns true on success.
+bool generate_sine(float frequency, const std::string & filename);
+
+} // namespace sine
+
+#endif // LIBSINE_H

Diff for: sine/src/CMakeLists.txt

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+add_library(libsine STATIC libsine.cpp ../include/libsine/libsine.h)
+
+target_include_directories(libsine PUBLIC ../include)
+
+target_compile_features(libsine PUBLIC cxx_std_11)
+
+target_link_libraries(libsine PRIVATE SndFile::sndfile)

Diff for: sine/src/libsine.cpp

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+#include <libsine/libsine.h>
+
+#include <cmath>
+#include <cstring>
+#include <vector>
+
+#include <sndfile.h>
+
+namespace sine
+{
+
+static constexpr int SampleRate = 44100;
+static constexpr int SampleCount = (SampleRate * 2); // 2 seconds
+static constexpr float Amplitude = (1.0 * 0x7F000000);
+
+// Based on libsndfile example:
+// https://github.com/erikd/libsndfile/blob/06ebde5/examples/make_sine.c
+bool generate_sine(float frequency, const std::string & filename)
+{
+    if (frequency < 0.0f) {
+        return false;
+    }
+
+    frequency /= SampleRate;
+
+    SF_INFO sfinfo;
+    memset(&sfinfo, 0, sizeof(sfinfo));
+    sfinfo.samplerate = 44100;
+    sfinfo.frames = SampleCount;
+    sfinfo.channels = 1;
+    sfinfo.format = (SF_FORMAT_WAV | SF_FORMAT_PCM_24);
+
+    SNDFILE * file = sf_open(filename.c_str(), SFM_WRITE, &sfinfo);
+    if (!file) {
+        return false;
+    }
+
+    std::vector<int> buffer(SampleCount);
+
+    for (int i = 0 ; i < SampleCount ; i++) {
+        buffer[i] = Amplitude * sin(frequency * 2 * i * M_PI);
+    }
+
+    if (sf_write_int(file, &buffer[0], sfinfo.channels * SampleCount) != sfinfo.channels * SampleCount) {
+        return false;
+    }
+
+    sf_close(file);
+
+    return true;
+}
+
+} // namespace sine