[libcamera-devel] [PATCH 05/16] libcamera: Separate source and build path helpers

[Kieran Bingham]

The libcameraSourcePath and libcameraBuildPath helper functions are
internal and specific to libcamera needs while operating with the meson
build system.

In preparation for the upcoming move of utils to a common library, move
these helpers out of utils and into their own build unit.

Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---
 include/libcamera/internal/meson.build    |   1 +
 include/libcamera/internal/source-paths.h |  19 ++++
 src/libcamera/meson.build                 |   1 +
 src/libcamera/source-paths.cpp            | 129 ++++++++++++++++++++++
 src/libcamera/utils.cpp                   | 102 -----------------
 5 files changed, 150 insertions(+), 102 deletions(-)
 create mode 100644 include/libcamera/internal/source-paths.h
 create mode 100644 src/libcamera/source-paths.cpp

diff --git a/include/libcamera/internal/meson.build b/include/libcamera/internal/meson.build
index f019cfb3b0de..e5088177fe8e 100644
--- a/include/libcamera/internal/meson.build
+++ b/include/libcamera/internal/meson.build
@@ -39,6 +39,7 @@ libcamera_internal_headers = files([
     'process.h',
     'pub_key.h',
     'semaphore.h',
+    'source-paths.h',
     'sysfs.h',
     'thread.h',
     'timer.h',
diff --git a/include/libcamera/internal/source-paths.h b/include/libcamera/internal/source-paths.h
new file mode 100644
index 000000000000..2591ebb1081b
--- /dev/null
+++ b/include/libcamera/internal/source-paths.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Google Inc.
+ *
+ * source-paths.h - Identify libcamera source and build paths
+ */
+#ifndef __LIBCAMERA_INTERNAL_SOURCE_PATHS_H__
+#define __LIBCAMERA_INTERNAL_SOURCE_PATHS_H__
+
+#include <string>
+
+namespace libcamera::utils {
+
+std::string libcameraBuildPath();
+std::string libcameraSourcePath();
+
+} /* namespace libcamera::utils */
+
+#endif /* __LIBCAMERA_INTERNAL_SOURCE_PATHS_H__ */
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index 387d20843203..e792094f5798 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -46,6 +46,7 @@ libcamera_sources = files([
     'request.cpp',
     'semaphore.cpp',
     'signal.cpp',
+    'source-paths.cpp',
     'stream.cpp',
     'sysfs.cpp',
     'thread.cpp',
diff --git a/src/libcamera/source-paths.cpp b/src/libcamera/source-paths.cpp
new file mode 100644
index 000000000000..b39f5f853e39
--- /dev/null
+++ b/src/libcamera/source-paths.cpp
@@ -0,0 +1,129 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Google Inc.
+ *
+ * source-paths.cpp - Identify libcamera source and build paths
+ */
+
+#include "libcamera/internal/source-paths.h"
+
+#include <dlfcn.h>
+#include <elf.h>
+#include <link.h>
+#include <sys/stat.h>
+
+#include "libcamera/internal/utils.h"
+
+/**
+ * \file source-paths.h
+ * \brief Identify the build and source path of a not-yet-installed library
+ */
+
+/* musl doesn't declare _DYNAMIC in link.h, declare it manually. */
+extern ElfW(Dyn) _DYNAMIC[];
+
+namespace libcamera::utils {
+
+/**
+ * \brief Check if libcamera is installed or not
+ *
+ * Utilise the build_rpath dynamic tag which is stripped out by meson at
+ * install time to determine at runtime if the library currently executing
+ * has been installed or not.
+ *
+ * \return True if libcamera is installed, false otherwise
+ */
+bool isLibcameraInstalled()
+{
+	/*
+	 * DT_RUNPATH (DT_RPATH when the linker uses old dtags) is removed on
+	 * install.
+	 */
+	for (const ElfW(Dyn) *dyn = _DYNAMIC; dyn->d_tag != DT_NULL; ++dyn) {
+		if (dyn->d_tag == DT_RUNPATH || dyn->d_tag == DT_RPATH)
+			return false;
+	}
+
+	return true;
+}
+
+/**
+ * \brief Retrieve the path to the build directory
+ *
+ * During development, it is useful to run libcamera binaries directly from the
+ * build directory without installing them. This function helps components that
+ * need to locate resources in the build tree, such as IPA modules or IPA proxy
+ * workers, by providing them with the path to the root of the build directory.
+ * Callers can then use it to complement or override searches in system-wide
+ * directories.
+ *
+ * If libcamera has been installed, the build directory path is not available
+ * and this function returns an empty string.
+ *
+ * \return The path to the build directory if running from a build, or an empty
+ * string otherwise
+ */
+std::string libcameraBuildPath()
+{
+	if (isLibcameraInstalled())
+		return std::string();
+
+	Dl_info info;
+
+	/* Look up our own symbol. */
+	int ret = dladdr(reinterpret_cast<void *>(libcameraBuildPath), &info);
+	if (ret == 0)
+		return std::string();
+
+	std::string path = dirname(info.dli_fname) + "/../../";
+
+	char *real = realpath(path.c_str(), nullptr);
+	if (!real)
+		return std::string();
+
+	path = real;
+	free(real);
+
+	return path + "/";
+}
+
+/**
+ * \brief Retrieve the path to the source directory
+ *
+ * During development, it is useful to run libcamera binaries directly from the
+ * build directory without installing them. This function helps components that
+ * need to locate resources in the source tree, such as IPA configuration
+ * files, by providing them with the path to the root of the source directory.
+ * Callers can then use it to complement or override searches in system-wide
+ * directories.
+ *
+ * If libcamera has been installed, the source directory path is not available
+ * and this function returns an empty string.
+ *
+ * \return The path to the source directory if running from a build directory,
+ * or an empty string otherwise
+ */
+std::string libcameraSourcePath()
+{
+	std::string path = libcameraBuildPath();
+	if (path.empty())
+		return std::string();
+
+	path += "source";
+
+	char *real = realpath(path.c_str(), nullptr);
+	if (!real)
+		return std::string();
+
+	path = real;
+	free(real);
+
+	struct stat statbuf;
+	int ret = stat(path.c_str(), &statbuf);
+	if (ret < 0 || (statbuf.st_mode & S_IFMT) != S_IFDIR)
+		return std::string();
+
+	return path + "/";
+}
+
+} /* namespace libcamera::utils */
diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp
index 49b8fc9e211f..42f82d6158dd 100644
--- a/src/libcamera/utils.cpp
+++ b/src/libcamera/utils.cpp
@@ -351,108 +351,6 @@ std::string toAscii(const std::string &str)
 	return ret;
 }
 
-/**
- * \brief Check if libcamera is installed or not
- *
- * Utilise the build_rpath dynamic tag which is stripped out by meson at
- * install time to determine at runtime if the library currently executing
- * has been installed or not.
- *
- * \return True if libcamera is installed, false otherwise
- */
-bool isLibcameraInstalled()
-{
-	/*
-	 * DT_RUNPATH (DT_RPATH when the linker uses old dtags) is removed on
-	 * install.
-	 */
-	for (const ElfW(Dyn) *dyn = _DYNAMIC; dyn->d_tag != DT_NULL; ++dyn) {
-		if (dyn->d_tag == DT_RUNPATH || dyn->d_tag == DT_RPATH)
-			return false;
-	}
-
-	return true;
-}
-
-/**
- * \brief Retrieve the path to the build directory
- *
- * During development, it is useful to run libcamera binaries directly from the
- * build directory without installing them. This function helps components that
- * need to locate resources in the build tree, such as IPA modules or IPA proxy
- * workers, by providing them with the path to the root of the build directory.
- * Callers can then use it to complement or override searches in system-wide
- * directories.
- *
- * If libcamera has been installed, the build directory path is not available
- * and this function returns an empty string.
- *
- * \return The path to the build directory if running from a build, or an empty
- * string otherwise
- */
-std::string libcameraBuildPath()
-{
-	if (isLibcameraInstalled())
-		return std::string();
-
-	Dl_info info;
-
-	/* Look up our own symbol. */
-	int ret = dladdr(reinterpret_cast<void *>(libcameraBuildPath), &info);
-	if (ret == 0)
-		return std::string();
-
-	std::string path = dirname(info.dli_fname) + "/../../";
-
-	char *real = realpath(path.c_str(), nullptr);
-	if (!real)
-		return std::string();
-
-	path = real;
-	free(real);
-
-	return path + "/";
-}
-
-/**
- * \brief Retrieve the path to the source directory
- *
- * During development, it is useful to run libcamera binaries directly from the
- * build directory without installing them. This function helps components that
- * need to locate resources in the source tree, such as IPA configuration
- * files, by providing them with the path to the root of the source directory.
- * Callers can then use it to complement or override searches in system-wide
- * directories.
- *
- * If libcamera has been installed, the source directory path is not available
- * and this function returns an empty string.
- *
- * \return The path to the source directory if running from a build directory,
- * or an empty string otherwise
- */
-std::string libcameraSourcePath()
-{
-	std::string path = libcameraBuildPath();
-	if (path.empty())
-		return std::string();
-
-	path += "source";
-
-	char *real = realpath(path.c_str(), nullptr);
-	if (!real)
-		return std::string();
-
-	path = real;
-	free(real);
-
-	struct stat statbuf;
-	int ret = stat(path.c_str(), &statbuf);
-	if (ret < 0 || (statbuf.st_mode & S_IFMT) != S_IFDIR)
-		return std::string();
-
-	return path + "/";
-}
-
 /**
  * \fn alignDown(unsigned int value, unsigned int alignment)
  * \brief Align \a value down to \a alignment
-- 
2.30.2