[PATCH V4 7/9] telemetry: support adding integer value as hexadecimal

[Morten Brørup]

> From: lihuisong (C) [mailto:lihuisong at huawei.com]
> Sent: Wednesday, 14 December 2022 03.44
> 
> 在 2022/12/14 1:09, Bruce Richardson 写道:
> > On Tue, Dec 13, 2022 at 06:15:10PM +0800, Huisong Li wrote:
> >> Sometimes displaying a unsigned integer value as hexadecimal encoded
> style
> >> is more expected for human consumption, such as, offload capability
> and
> >> device flag. This patch introduces two APIs to add unsigned integer
> (can be
> >> one of uint8_t, uint16_t, uint32_t and uint64_t type) value as
> hexadecimal
> >> encoded string to array or dictionary. If the 'val_bits' is zero,
> the value
> >> is stored as hexadecimal encoded string without padding zero.
> >>
> >> Signed-off-by: Huisong Li <lihuisong at huawei.com>
> >> Acked-by: Morten Brørup <mb at smartsharesystems.com>
> >> Acked-by: Chengwen Feng <fengchengwen at huawei.com>
> > Thanks for the patch. Agree with the principle of it, but some
> comments
> > inline.
> >
> > /Bruce
> >
> >> ---
> >>   lib/telemetry/rte_telemetry.h  | 50 +++++++++++++++++++++++++++++
> >>   lib/telemetry/telemetry_data.c | 58
> ++++++++++++++++++++++++++++++++++
> >>   lib/telemetry/version.map      |  9 ++++++
> >>   3 files changed, 117 insertions(+)
> >>
> >> diff --git a/lib/telemetry/rte_telemetry.h
> b/lib/telemetry/rte_telemetry.h
> >> index 40e9a3bf9d..88b34097b0 100644
> >> --- a/lib/telemetry/rte_telemetry.h
> >> +++ b/lib/telemetry/rte_telemetry.h
> >> @@ -10,6 +10,7 @@ extern "C" {
> >>   #endif
> >>
> >>   #include <stdint.h>
> >> +#include <rte_compat.h>
> >>
> >>   /** Maximum length for string used in object. */
> >>   #define RTE_TEL_MAX_STRING_LEN 128
> >> @@ -20,6 +21,11 @@ extern "C" {
> >>   /** Maximum number of array entries. */
> >>   #define RTE_TEL_MAX_ARRAY_ENTRIES 512
> >>
> >> +#define RTE_TEL_U8_BITS  8
> >> +#define RTE_TEL_U16_BITS 16
> >> +#define RTE_TEL_U32_BITS 32
> >> +#define RTE_TEL_U64_BITS 64
> >> +
> > Not sure these are really necessary, but fairly harmless I suppose.
> This is convenient for the user to use.
> >
> >>   /**
> >>    * @file
> >>    *
> >> @@ -153,6 +159,27 @@ int
> >>   rte_tel_data_add_array_container(struct rte_tel_data *d,
> >>   		struct rte_tel_data *val, int keep);
> >>
> >> +/**
> >> + * Convert a unsigned integer to hexadecimal encoded strings and
> add this string
> >> + * to an array.
> >> + * The array must have been started by rte_tel_data_start_array()
> with
> >> + * RTE_TEL_STRING_VAL as the type parameter.
> >> + *
> >> + * @param d
> >> + *   The data structure passed to the callback
> >> + * @param val
> >> + *   The number to be returned in the array as a hexadecimal
> encoded strings.
> >> + *   The type of ''val' can be one of uint8_t, uint16_t, uint32_t
> and uint64_t.
> > Not sure this last line needs to be stated.
> >
> >> + * @param val_bits
> >> + *   The total bits of the input 'val'. If val_bits is zero, the
> value is stored
> >> + *   in the array as hexadecimal encoded string without padding
> zero.
> >> + * @return
> >> + *   0 on success, negative errno on error
> >> + */
> >> +__rte_experimental
> >> +int rte_tel_data_add_array_uint_hex(struct rte_tel_data *d,
> uint64_t val,
> >> +				    uint16_t val_bits);
> >> +
> > Just watch for whitespace consistency and coding standards. The "int"
> > should be on  a line by itself, so the function name always starts in
> > column 0 of a line.
> Sorry, I refer to a wrong example.
> >
> > I would also suggest renaming "val_bits" - maybe "display_bitwidth"
> would
> > be clearer, though also rather long.
> The 'val_bits' means the total bits of input 'val', It also reflects
> the
> type of data
> to be stored in hexadecimal. After all, we use 'u64' to cover all
> unisgned integer types.
> And this function is introduced for adding hexadecimal format value,
> not
> binary format.
> The value can not be stored exactly according to the input
> "display_bitwidth".
> If we limit to only 8/16/32/64 integer types, the 'val_bits' is better,
> I think.

NAK to limiting the bitwidth to 8/16/32/64 bits!

The function should be able to dump bitfields, such as the TCP flags, where the bitwidth is 6.

> >
> >>   /**
> >>    * Add a string value to a dictionary.
> >>    * The dict must have been started by rte_tel_data_start_dict().
> >> @@ -231,6 +258,29 @@ int
> >>   rte_tel_data_add_dict_container(struct rte_tel_data *d, const char
> *name,
> >>   		struct rte_tel_data *val, int keep);
> >>
> >> +/**
> >> + * Convert a unsigned integer to hexadecimal encoded strings and
> add this string
> >> + * to an dictionary.
> >> + * The dict must have been started by rte_tel_data_start_dict().
> >> + *
> >> + * @param d
> >> + *   The data structure passed to the callback
> >> + * @param name
> >> + *   The name of the value is to be stored in the dict
> >> + *   Must contain only alphanumeric characters or the symbols: '_'
> or '/'
> >> + * @param val
> >> + *   The number to be stored in the dict as a hexadecimal encoded
> strings.
> >> + *   The type of ''val' can be one of uint8_t, uint16_t, uint32_t
> and uint64_t.
> >> + * @param val_bits
> >> + *   The total bits of the input 'val'. If val_bits is zero, the
> value is stored
> >> + *   in the array as hexadecimal encoded string without padding
> zero.
> >> + * @return
> >> + *   0 on success, negative errno on error
> >> + */
> >> +__rte_experimental
> >> +int rte_tel_data_add_dict_uint_hex(struct rte_tel_data *d, const
> char *name,
> >> +				   uint64_t val, uint16_t val_bits);
> >> +
> > same comments as above.
> >
> >>   /**
> >>    * This telemetry callback is used when registering a telemetry
> command.
> >>    * It handles getting and formatting information to be returned to
> telemetry
> >> diff --git a/lib/telemetry/telemetry_data.c
> b/lib/telemetry/telemetry_data.c
> >> index 080d99aec9..fb2f711d99 100644
> >> --- a/lib/telemetry/telemetry_data.c
> >> +++ b/lib/telemetry/telemetry_data.c
> >> @@ -4,6 +4,7 @@
> >>
> >>   #include <errno.h>
> >>   #include <stdlib.h>
> >> +#include <inttypes.h>
> >>
> >>   #undef RTE_USE_LIBBSD
> >>   #include <stdbool.h>
> >> @@ -12,6 +13,9 @@
> >>
> >>   #include "telemetry_data.h"
> >>
> >> +#define RTE_TEL_UINT_HEX_STRING_BUFFER_LEN 64
> >> +#define RTE_TEL_UINT_HEX_FORMAT_LEN 16
> >> +
> >>   int
> >>   rte_tel_data_start_array(struct rte_tel_data *d, enum
> rte_tel_value_type type)
> >>   {
> >> @@ -113,6 +117,33 @@ rte_tel_data_add_array_container(struct
> rte_tel_data *d,
> >>   	return 0;
> >>   }
> >>
> >> +int
> >> +rte_tel_data_add_array_uint_hex(struct rte_tel_data *d, uint64_t
> val,
> >> +				uint16_t val_bits)
> >> +{
> >> +	char hex_str[RTE_TEL_UINT_HEX_STRING_BUFFER_LEN];
> >> +
> >> +	switch (val_bits) {
> >> +	case RTE_TEL_U8_BITS:
> >> +		sprintf(hex_str, "0x%02"PRIx64"", val);
> >> +		break;
> >> +	case RTE_TEL_U16_BITS:
> >> +		sprintf(hex_str, "0x%04"PRIx64"", val);
> >> +		break;
> >> +	case RTE_TEL_U32_BITS:
> >> +		sprintf(hex_str, "0x%08"PRIx64"", val);
> >> +		break;
> >> +	case RTE_TEL_U64_BITS:
> >> +		sprintf(hex_str, "0x%016"PRIx64"", val);
> >> +		break;
> >> +	default:
> >> +		sprintf(hex_str, "0x%"PRIx64"", val);
> >> +		break;
> >> +	}
> >> +
> >> +	return rte_tel_data_add_array_string(d, hex_str);
> >> +}
> >> +
> > This assume we only want those power-of-2 sizes. Is there a reason
> why we
> > can't use the code suggested by Morten in the discussion on v3?
> Having the
> > extra flexibility might be nice if we can get it.
> The compiler doesn't like it. There is a warning:
> 'warning: format not a string literal, argument types not checked
> [-Wformat-nonliteral]'

You can surround the affected functions by some #pragma to temporarily disable that warning.

I assume you noticed the bugs in my code:

char str[64]; // FIXME: Use correct size.
if (bits != 0) {
  char format[16]; // FIXME: Use correct size.
  sprintf(format, "0x%%0%u" PRIx64, (bits + 3) / 4); // bug fixed here
  sprintf(str, format, value);
} else {
  sprintf(str, "0x%" PRIx64, value);
}


> >
> > If we do need to limit to only 8/16/32/64, then I recommend using an
> enum
> > in the header rather than #defines for those values. That makes it
> clearer
> > that only a very limited range is supported.
> >
> > Also, code above treats all values other than 8/16/32/64 as if they
> were 0.
> > If 20, for example, is passed, we probably want to return error
> rather than
> > treating it as zero.
> I have to only consider 8/16/32/64 integer types because of above
> warning.
> In addition, the normal unsigned integer data is one of them. If user
> forces
> '0xf1f23' value to 10 bitwidth to display, it will be truncated as
> 0xf23.

The printf width field specifies the MINIMUM number of characters to output.

Truncation would be a bug in the C library.

> It seems pointless and unfriendly.
> So overall, this function is limited to all uint types, and is
> currently
> fully adequate.
> 
> Do we need to check other bitwidth? If the 'val_bits' isn't 8/16/32/64,
> it is processed as
> no-padding zero.