All it is used for is corralling an HTTP request response into something a bit safer and more flexible than a bare manually managed c-string.

Therefore I will be considering safety concerns, if you don't mind.

string_buffer.h

1. __cplusplus: I don't know whether this string library is used in C++ too or not. Either way, I would personally avoid that: C++ has std::string. And if, for some reason, you are using this library to handle strings...just don't again. std::string is likely to outperform your library.

2. StringBuffer declaration: You can omit the struct name when using typedef. I changed len and cap to length and  capacity, as they look clearer. typedef struct { char* str; size_t length; size_t capacity; char small_str[64]; } StringBuffer;

string_buffer.cpp

1. I do like the small_str which cuts down on small allocations.
   When you realloc the pointer, though, you just ask for min_cap. After the memcpy, length == capacity. Thus, I would recommend you to allocate more bytes e.g. min_cap + sizeof(small_str)*. You can find this useful if the library often handles big strings.

*I would turn sizeof(small_str) into a constant, kind of default_size, since it appears frequently.

Overall design

1. There is no check for NULL pointers. That's gonna lead to lots of  SIGSEGVs if you accidentally forget to call string_buffer_init, for example.
2. It's important to point out that you're actually using a function which belongs to an external library. Nevertheless, I'd go for:

• stringbuffer
• stringBuffer
• sb
  rather than string_builder. It should be a compact name; consider e.g. glPushMatrix() or alcOpenDevice.*/

All it is used for is corralling an HTTP request response into something a bit safer and more flexible than a bare manually managed C-string.

Therefore I will be considering safety concerns, if you don't mind.

string_buffer.h

1. __cplusplus: I don't know whether this string library is used in C++ too or not. Either way, I would personally avoid that: C++ has std::string. And if, for some reason, you are using this library to handle strings...just don't again. std::string is likely to outperform your library.

2. StringBuffer declaration: You can omit the struct name when using typedef. I changed len and cap to length and  capacity, as they look clearer.

   typedef struct {
       char* str;
       size_t length;
       size_t capacity;
       char small_str[64];
   } StringBuffer;
   

string_buffer.cpp

1. I do like the small_str which cuts down on small allocations. When you realloc the pointer, though, you just ask for min_cap. After the memcpy, length == capacity.

Thus, I would recommend you to allocate more bytes e.g. min_cap + sizeof(small_str) ^*. You can find this useful if the library often handles big strings.

^* I would turn sizeof(small_str) into a constant, kind of like default_size, since it appears frequently.

Overall design

1. There is no check for NULL pointers. That's gonna lead to lots of  SIGSEGVs if you accidentally forget to call string_buffer_init, for example.
2. It's important to point out that you're actually using a function which belongs to an external library.

Nevertheless, I'd go for:

• stringbuffer

• stringBuffer

• sb rather than string_builder.

  It should be a compact name; consider e.g. glPushMatrix() or alcOpenDevice.