On Mon, 7 Jun 2010 15:42:16 +0100
"Daniel P. Berrange" <berra...@redhat.com> wrote:
> There is quite alot of code using an enumeration of possible
> values, which also needs todo conversions to/from a string
> representation of enum values. These string <-> int conversions
> have been repeated in an adhoc manner throughout the code.
>
> This makes it hard to report on the list of valid strings,
> eg in help output, or todo proper validation in the qemu
> config/option parsing routines.
>
> This addresses the first problem by introducing a standard
> set of routines for performing string <-> int conversions
> for enums. There are two restrictions on using these helpers,
> the first enum value must be 0, and there must be a sentinal
> in the enum to provide the max value.
>
> For each enumeration, three functions will be made available
>
> - string to int convertor:
>
> int XXXX_from_string(const char *value);
>
> Returns -1 if the value was not an allowed string for the
> enumeration. Returns >= 0 for a valid value
>
> - int to string convertor
>
> const char * XXXX_to_string(int value);
>
> Returns NULL if the value was not a member of the
> enumeration. Returns a non-NULL sstring for valid value
>
> - string list generator
>
> char * XXXX_to_string_list(void);
>
> Returns a malloc'd string containing all valid values,
> separated by commas. Caller must free the string.
>
> The general usage pattern is as follows.
>
> In the header file (eg qemu-option.h):
>
> enum QemuOptType {
> QEMU_OPT_STRING = 0, /* no parsing (use string as-is)
> */
> QEMU_OPT_BOOL, /* on/off
> */
> QEMU_OPT_NUMBER, /* simple number
> */
> QEMU_OPT_SIZE, /* size, accepts (K)ilo, (M)ega, (G)iga, (T)era
> postfix */
>
> QEMU_OPT_LAST
> };
> QEMU_ENUM_DECL(qemu_opt_type);
>
> This declares the function prototypes for the 3 methods
> outlined above.
>
> In the corresponding source file (eg qemu-option.c):
>
> QEMU_ENUM_IMPL(qemu_opt_type,
> QEMU_OPT_LAST,
> "string", "bool", "number", "size");
>
> This provides the implementation of the 3 methods. If there
> are greater/fewer strings provided than the number of values
> in the enumeration, this generates a compile time assertion
> failure that looks like
>
> qemu-option.c:35: error: negative width in bit-field
> ‘verify_error_if_negative_size__’
>
> Signed-off-by: Daniel P. Berrange <berra...@redhat.com>
> ---
> Makefile.objs | 2 +-
> qemu-enum.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> qemu-enum.h | 45 +++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 90 insertions(+), 1 deletions(-)
> create mode 100644 qemu-enum.c
> create mode 100644 qemu-enum.h
>
> diff --git a/Makefile.objs b/Makefile.objs
> index 9796dcb..0ba9966 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -8,7 +8,7 @@ qobject-obj-y += qerror.o
> # block-obj-y is code used by both qemu system emulation and qemu-img
>
> block-obj-y = cutils.o cache-utils.o qemu-malloc.o qemu-option.o module.o
> -block-obj-y += nbd.o block.o aio.o aes.o osdep.o qemu-config.o
> +block-obj-y += nbd.o block.o aio.o aes.o osdep.o qemu-config.o qemu-enum.o
> block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
> block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
>
> diff --git a/qemu-enum.c b/qemu-enum.c
> new file mode 100644
> index 0000000..9bb33ac
> --- /dev/null
> +++ b/qemu-enum.c
> @@ -0,0 +1,44 @@
> +#include "qemu-enum.h"
Missing license text.
> +
> +int qemu_enum_from_string(const char *const*types,
> + unsigned int ntypes,
> + const char *type)
> +{
> + unsigned int i;
> + if (!type)
> + return -1;
> +
> + for (i = 0 ; i < ntypes ; i++)
> + if (strcmp(types[i], type) == 0)
> + return i;
> +
> + return -1;
> +}
> +
> +const char *qemu_enum_to_string(const char *const*types,
> + unsigned int ntypes,
> + int type)
> +{
> + if (type < 0 || type >= ntypes)
> + return NULL;
> +
> + return types[type];
> +}
> +
> +char *qemu_enum_to_string_list(const char *const*types,
> + unsigned int ntypes)
> +{
> + size_t len = 0;
> + char *ret;
> + int i;
> + for (i = 0 ; i < ntypes ; i++)
> + len += strlen(types[i]) + 2;
> + ret = qemu_malloc(len);
> + *ret = '\0';
> + for (i = 0 ; i < ntypes ; i++) {
> + if (i > 0)
> + strcat(ret, ", ");
> + strcat(ret, types[i]);
> + }
> + return ret;
> +}
> diff --git a/qemu-enum.h b/qemu-enum.h
> new file mode 100644
> index 0000000..ff47798
> --- /dev/null
> +++ b/qemu-enum.h
> @@ -0,0 +1,45 @@
> +#ifndef QEMU_ENUM_H
> +#define QEMU_ENUM_H
> +
> +#include "qemu-common.h"
> +#include "verify.h"
> +
> +
> +int qemu_enum_from_string(const char *const*types,
> + unsigned int ntypes,
> + const char *type);
> +
> +const char *qemu_enum_to_string(const char *const*types,
> + unsigned int ntypes,
> + int type);
> +
> +char *qemu_enum_to_string_list(const char *const*types,
> + unsigned int ntypes);
> +
> +#define QEMU_ENUM_IMPL(name, lastVal, ...) \
> + static const char *const name ## _string_list[] = { __VA_ARGS__ };
> \
> + char *name ## _to_string_list(void) { \
> + return qemu_enum_to_string_list(name ## _string_list,
> \
> + ARRAY_SIZE(name ## _string_list)); \
> + } \
> + const char *name ## _to_string(int type) {
> \
> + return qemu_enum_to_string(name ## _string_list, \
> + ARRAY_SIZE(name ## _string_list), \
> + type); \
> + } \
> + int name ## _from_string(const char *type) { \
> + return qemu_enum_from_string(name ## _string_list, \
> + ARRAY_SIZE(name ## _string_list), \
> + type); \
> + }
> \
> + extern int (* name ## Verify (void)) \
> + [verify_true (ARRAY_SIZE(name ## _string_list) == lastVal)]
> +
> +# define QEMU_ENUM_DECL(name) \
> + const char *name ## _to_string(int type); \
> + char *name ## _to_string_list(void); \
> + int name ## _from_string(const char*type)
> +
> +
> +
> +#endif /* QEMU_ENUM_H */
