Add python.c.

Patch by: Jonathan Callen

1 files changed, 203 insertions, 0 deletions

diff --git a/python.c b/python.c
new file mode 100644
index 0000000..dd1bc8b
--- /dev/null
+++ b/python.c
@@ -0,0 +1,203 @@
+/* Copyright 1999-2009 Gentoo Foundation
+ * Distributed under the terms of the GNU General Public License v2
+ */
+#include <dirent.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/stat.h>
+
+#define ENVD_CONFIG "/etc/env.d/python/config"
+
+/* 127 is the standard return code for "command not found" */
+#define EXIT_ERROR 127
+
+char* dir_cat(const char* dir, const char* file)
+{
+	size_t dir_len = strlen(dir);
+	char* abs = malloc(dir_len + strlen(file) + 2);
+	strcpy(abs, dir);
+	abs[dir_len] = '/';
+	abs[dir_len + 1] = 0;
+	return strcat(abs, file);
+}
+
+const char* find_path(const char* exe)
+{
+	const char* last_slash = strrchr(exe, '/');
+	if (last_slash)
+	{
+		return strndup(exe, last_slash - exe);
+	}
+	char* path = strdup(getenv("PATH"));
+	char* state;
+	const char* token = strtok_r(path, ":", &state);
+	while (token)
+	{
+		/* If an element of PATH is empty ("::"), then it is "." */
+		if (! *token)
+		{
+			token = ".";
+		}
+		/* If it starts with "~/", use "${HOME}/" instead */
+		if (strncmp(token, "~/", 2) == 0)
+		{
+			char* home = getenv("HOME");
+			char* new_token = malloc(strlen(token) + strlen(home));
+			strcpy(new_token, home);
+			strcat(new_token, token + 1);
+			token = new_token;
+		}
+		struct stat sbuf;
+		char* str = dir_cat(token, exe);
+		if (stat(str, &sbuf) == 0 && (S_ISREG(sbuf.st_mode) || S_ISLNK(sbuf.st_mode)))
+		{
+			return token;
+		}
+		token = strtok_r(NULL, ":", &state);
+	}
+	return NULL;
+}
+
+/* True if a valid file name, and not "python" */
+int valid_interpreter(const char* name)
+{
+	if (! name || ! *name || (strcmp(name, "python") == 0))
+	{
+		return 0;
+	}
+	return 1;
+}
+
+int get_version(const char* name)
+{
+	/* Only find files beginning with "python" - this is a fallback,
+	 * so we only want CPython
+	 */
+	if (! valid_interpreter(name) || strncmp(name, "python", 6) != 0)
+		return -1;
+	int pos = 6;
+	int major = 0;
+	int minor = 0;
+	if (name[pos] < '0' || name[pos] > '9')
+		return -1;
+	do
+	{
+		major = major * 10 + name[pos] - '0';
+		if (! name[++pos])
+			return -1;
+	}
+	while (name[pos] >= '0' && name[pos] <= '9');
+	if (name[pos++] != '.')
+		return -1;
+	if (name[pos] < '0' || name[pos] > '9')
+		return -1;
+	do
+	{
+		minor = minor * 10 + name[pos] - '0';
+		if (! name[++pos])
+			return (major << 8) | minor;
+	}
+	while (name[pos] >= '0' && name[pos] <= '9');
+	return -1;
+}
+
+int filter_python(const struct dirent* file)
+{
+	return get_version(file->d_name) != -1;
+}
+
+/* This implements a version sort, such that the following order applies:
+ *    <invalid file names> (should never be seen)
+ *    python2.6
+ *    python2.9
+ *    python2.10
+ *    python3.0
+ *    python3.1
+ *    python3.2
+ *    python9.1
+ *    python9.9
+ *    python9.10
+ *    python10.1
+ *    python10.9
+ *    python10.10
+ */
+int sort_python(const struct dirent**f1, const struct dirent** f2)
+{
+	int ver1 = get_version((*f1)->d_name);
+	int ver2 = get_version((*f2)->d_name);
+	return ver1 - ver2;
+}
+
+const char* find_latest(const char* exe)
+{
+	int major = -1;
+	int minor = -1;
+	const char* path = find_path(exe);
+	if (! path || ! *path)
+	{
+		path = "/usr/bin";
+	}
+	struct dirent** namelist;
+	int n = scandir(path, &namelist, filter_python, sort_python);
+	const char* ret = NULL;
+	if (n < 0)
+	{
+		return NULL;
+	}
+	/* walk backwards through the list */
+	while (n--)
+	{
+		if (! ret)
+			ret = strdup(namelist[n]->d_name);
+		free(namelist[n]);
+	}
+	free(namelist);
+	return ret;
+}
+
+int main(int argc, char** argv)
+{
+	const char* EPYTHON = getenv("EPYTHON");
+	if (! valid_interpreter(EPYTHON))
+	{
+		FILE* f = fopen(ENVD_CONFIG, "r");
+		if (f)
+		{
+			struct stat st;
+			fstat(fileno(f), &st);
+			size_t size = st.st_size;
+			char* cont = malloc(size + 1);
+			fgets(cont, size + 1, f);
+			fclose(f);
+			size_t len = strlen(cont);
+			if (len && cont[len - 1] == '\n')
+				cont[len - 1] = 0;
+			EPYTHON = cont;
+		}
+	}
+
+	if (! valid_interpreter(EPYTHON))
+		EPYTHON = find_latest(argv[0]);
+
+	if (! EPYTHON)
+		return EXIT_ERROR;
+
+	if (strchr(EPYTHON, '/'))
+	{
+		execv(EPYTHON, argv);
+		return EXIT_ERROR;
+	}
+
+	const char* path = find_path(argv[0]);
+	if (*path)
+	{
+		execv(dir_cat(path, EPYTHON), argv);
+		return EXIT_ERROR;
+	}
+
+	execvp(EPYTHON, argv);
+	return EXIT_ERROR;
+}