Need help regarding string replacement in a tag file

[ethan]

I need to delete a string : (png_structp png_ptr,$/;"
fin the tag
PNG_EXTERN void png_write_sCAL_s PNGARG((png_structp png_ptr,$/;"
and replace it with
(png_structp png_ptr, int unit, png_const_charp width, png_const_charp
height)

expected output should be like this :
PNG_EXTERN void png_write_sCAL_s PNGARG((png_structp png_ptr, int
unit, png_const_charp width, png_const_charp height));

but the script should also take care of the function call also...

like in
PNG_EXTERN size_t png_safecat(png_charp buffer, size_t bufsize, size_t
pos,$/;" signature:(png_charp buffer, size_t bufsize, size_t pos,
png_const_charp string)

the string
(png_charp buffer, size_t bufsize, size_t pos,$/;" should be replaced
with
(png_charp buffer, size_t bufsize, size_t pos, png_const_charp string)

output like:
PNG_EXTERN size_t png_safecat(png_charp buffer, size_t bufsize, size_t
pos, png_const_charp string);