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tlv: add TLV_GET() and TLV_GET_MINLEN() 

Rationale: so far we use code like

  if (TLVP_PRESENT(&tp, VERY_LONG_ENUM_VALUE_NAME_THAT_NEVER_ENDS)) {
  	val = TLVP_VAL(&tp, VERY_LONG_ENUM_VALUE_NAME_THAT_NEVER_ENDS);
	len = TLVP_LEN(&tp, VERY_L0NG_ENUM_VALUE_NAME_TH4T_NEVER_EMDS);
  }

This is a) very long and b) prone to picking the wrong name one of the three
times, which would use the wrong length or val without necessarily being
noticed. A safer and shorter, more readable pattern is:

  struct tlv_p_entry *e = TVLP_GET(&tp, VERY_LONG_ENUM_VALUE_NAME_THAT_NEVER_ENDS);
  if (!e)
        return -ENOENT;
  hexdump(e->val, e->len);

Change-Id: I445de17fc2daa3ab051f5708dd0cc185b23dc048
This commit is contained in:
Neels Hofmeyr 2018-04-13 03:55:06 +02:00
parent 8d41d722d6
commit 74e4ed6f36
1 changed files with 21 additions and 0 deletions
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21
include/osmocom/gsm/tlv.h
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@ -446,6 +446,27 @@ void tlv_def_patch(struct tlv_definition *dst, const struct tlv_definition *src)
#define TLVP_PRES_LEN(tp, tag, min_len) \
(TLVP_PRESENT(tp, tag) && TLVP_LEN(tp, tag) >= min_len)
/*! Return pointer to a TLV element if it is present.
* Usage:
* struct tlv_p_entry *e = TVLP_GET(&tp, TAG);
* if (!e)
* return -ENOENT;
* hexdump(e->val, e->len);
* \param[in] _tp pointer to \ref tlv_parsed.
* \param[in] tag IE tag to return.
* \returns struct tlv_p_entry pointer, or NULL if not present.
*/
#define TLVP_GET(_tp, tag) (TLVP_PRESENT(_tp, tag)? &(_tp)->lv[tag] : NULL)
/*! Like TLVP_GET(), but enforcing a minimum val length.
* \param[in] _tp pointer to \ref tlv_parsed.
* \param[in] tag IE tag to return.
* \param[in] min_len Minimum value length in bytes.
* \returns struct tlv_p_entry pointer, or NULL if not present or too short.
*/
#define TLVP_GET_MINLEN(_tp, tag, min_len) \
(TLVP_PRES_LEN(_tp, tag, min_len)? &(_tp)->lv[tag] : NULL)
/*! Align given TLV element with 16 bit value to an even address
* \param[in] tp pointer to \ref tlv_parsed
* \param[in] pos element to return