[PATCH V2 04/22] util: env var helpers

[Steve Sistare]

Add functions for saving fd's and other values in the environment via
setenv, and for reading them back via getenv.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Signed-off-by: Mark Kanda <mark.kanda@oracle.com>
---
 include/qemu/env.h |  27 ++++++++++++
 util/Makefile.objs |   2 +-
 util/env.c         | 119 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 147 insertions(+), 1 deletion(-)
 create mode 100644 include/qemu/env.h
 create mode 100644 util/env.c

diff --git a/include/qemu/env.h b/include/qemu/env.h
new file mode 100644
index 0000000..174f0c7
--- /dev/null
+++ b/include/qemu/env.h
@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2021 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef QEMU_ENV_H
+#define QEMU_ENV_H
+
+#define FD_PREFIX "QEMU_FD_"
+#define BOOL_PREFIX "QEMU_BOOL_"
+
+typedef int (*walkenv_cb)(const char *name, const char *val, void *handle);
+
+int getenv_fd(const char *name);
+void setenv_fd(const char *name, int fd);
+void unsetenv_fd(const char *name);
+void unsetenv_fdv(const char *fmt, ...);
+bool getenv_bool(const char *name);
+void setenv_bool(const char *name, bool val);
+void unsetenv_bool(const char *name);
+int walkenv(const char *prefix, walkenv_cb cb, void *handle);
+void printenv(void);
+
+#endif
diff --git a/util/Makefile.objs b/util/Makefile.objs
index cc5e371..d357932 100644
--- a/util/Makefile.objs
+++ b/util/Makefile.objs
@@ -1,4 +1,4 @@
-util-obj-y = osdep.o cutils.o unicode.o qemu-timer-common.o
+util-obj-y = osdep.o cutils.o unicode.o qemu-timer-common.o env.o
 util-obj-$(call lnot,$(CONFIG_ATOMIC64)) += atomic64.o
 util-obj-$(CONFIG_POSIX) += aio-posix.o
 util-obj-$(CONFIG_POSIX) += fdmon-poll.o
diff --git a/util/env.c b/util/env.c
new file mode 100644
index 0000000..afaf77f
--- /dev/null
+++ b/util/env.c
@@ -0,0 +1,119 @@
+/*
+ * Copyright (c) 2021 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/env.h"
+
+static uint64_t getenv_ulong(const char *prefix, const char *name, bool *found)
+{
+    char var[80], *val;
+    uint64_t res;
+
+    snprintf(var, sizeof(var), "%s%s", prefix, name);
+    val = getenv(var);
+    if (val) {
+        *found = true;
+        res = strtol(val, 0, 10);
+    } else {
+        *found = false;
+        res = 0;
+    }
+    return res;
+}
+
+static void setenv_ulong(const char *prefix, const char *name, uint64_t val)
+{
+    char var[80], val_str[80];
+    snprintf(var, sizeof(var), "%s%s", prefix, name);
+    snprintf(val_str, sizeof(val_str), "%"PRIu64, val);
+    setenv(var, val_str, 1);
+}
+
+static void unsetenv_ulong(const char *prefix, const char *name)
+{
+    char var[80];
+    snprintf(var, sizeof(var), "%s%s", prefix, name);
+    unsetenv(var);
+}
+
+int getenv_fd(const char *name)
+{
+    bool found;
+    int fd = getenv_ulong(FD_PREFIX, name, &found);
+    if (!found) {
+        fd = -1;
+    }
+    return fd;
+}
+
+void setenv_fd(const char *name, int fd)
+{
+    setenv_ulong(FD_PREFIX, name, fd);
+}
+
+void unsetenv_fd(const char *name)
+{
+    unsetenv_ulong(FD_PREFIX, name);
+}
+
+void unsetenv_fdv(const char *fmt, ...)
+{
+    va_list args;
+    char buf[80];
+    va_start(args, fmt);
+    vsnprintf(buf, sizeof(buf), fmt, args);
+    va_end(args);
+}
+
+bool getenv_bool(const char *name)
+{
+    bool found;
+    bool val = getenv_ulong(BOOL_PREFIX, name, &found);
+    if (!found) {
+        val = -1;
+    }
+    return val;
+}
+
+void setenv_bool(const char *name, bool val)
+{
+    setenv_ulong(BOOL_PREFIX, name, val);
+}
+
+void unsetenv_bool(const char *name)
+{
+    unsetenv_ulong(BOOL_PREFIX, name);
+}
+
+int walkenv(const char *prefix, walkenv_cb cb, void *handle)
+{
+    char *str, name[128];
+    char **envp = environ;
+    size_t prefix_len = strlen(prefix);
+
+    while (*envp) {
+        str = *envp++;
+        if (!strncmp(str, prefix, prefix_len)) {
+            char *val = strchr(str, '=');
+            str += prefix_len;
+            strncpy(name, str, val - str);
+            name[val - str] = 0;
+            if (cb(name, val + 1, handle)) {
+                return 1;
+            }
+        }
+    }
+    return 0;
+}
+
+void printenv(void)
+{
+    char **ptr = environ;
+    while (*ptr) {
+        puts(*ptr++);
+    }
+}
-- 
1.8.3.1