c-function to find a simple pattern CHnnnnnX do not use RegEx

Routine must be pure C (not C++). Routine must find in a string a pattern The pattern is <nobr>CHnnnnnnnX</nobr> n stand for a number 0-9 X stand for 1-12 characters 0-9 a-z A-Z Routine should be fast and not use libraries like a RegEx Library. postivie examples: string = "bla bla <nobr>CH1000123A1BC</nobr> more bla bla" string = "<nobr>CH9912345123456789012</nobr>" negativ examples string = "bla bla <nobr>XX9912345123</nobr>" string = "<nobr>CHF</nobr>" string = "<nobr>CH1212345AAAABBBBCCCC1</nobr> ## Deliverables Just to add nnnnnnn is a fixed length of 7 numeric characters. X is variable length from 1 to 12 alphanumeric characters.