Add read_number public functions

[pavelxdd]

I really like the yyjson read_number implementation and want to use it in my projects. The problem is that the current implementation is a static function which can't be used from other code.

I've added a simple wrapper unsafe_yyjson_read_number around read_number function, which parses number from the memory buffer into yyjson_val (or yyjson_mut_val) variable.

[codecov[bot]]

Codecov Report

Merging #97 (2ccd693) into master (b2a6dfe) will increase coverage by 0.00%. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #97   +/-   ##
=======================================
  Coverage   98.41%   98.42%           
=======================================
  Files           2        2           
  Lines        2335     2347   +12     
=======================================
+ Hits         2298     2310   +12     
  Misses         37       37           

Impacted Files	Coverage Δ
src/yyjson.h	87.05% <ø> (ø)
src/yyjson.c	98.85% <100.00%> (+<0.01%)	:arrow_up:

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[pavelxdd]

I've updated the commit with following changes:

1) Removed unsafe_yyjson_read_number in favor of yyjson_read_number. yyjson_mut_read_number is just a wrapper around yyjson_read_number.

2) Return end pointer instead of boolean if parsing was successful, or return NULL instead.

3) Support yyjson_read_err optional parameter.

[pavelxdd]

https://github.com/ibireme/yyjson/blob/b2a6dfeb9c89cc53adc6203896a66850a5973373/src/yyjson.c#L3508

The current error message is misleading if no zero sign is present in buffer. For example .123 gives this message, and sets the cur to hdr - 1, so we can't safely cur - hdr after this error.

Hence, I've added a _pos > hdr check in return_err macro.

[pavelxdd]

I've added test cases based on test_number text files.

Also added support for YYJSON_READ_NUMBER_AS_RAW and YYJSON_READ_ALLOW_INF_AND_NAN read flags.

[ibireme]

Thanks, it looks much better now~