The C API in Practice

What you have seen so far will take you a long way. If you want to understand what is going on in more detail, understand proper error handling, or work with binary data, however, we need to drop down a level and look at the API in a practical example. To these ends, we will look to an API that provides callers with access to delayed stock quotes stored in a MySQL database. The application leverages a single MySQL table, Stock, with the following schema: 

CREATE TABLE Stock (
    symbol    CHAR(5) NOT NULL PRIMARY KEY,
    openPrice REAL    NOT NULL,
    currPrice REAL    NOT NULL,
    high52    REAL    NOT NULL,
    low52     REAL    NOT NULL
);

Our library needs two basic functions:

void assign_stock(Stock *stock);

Assigns the values in the Stock structure to the database

Stock *get_stock(char *symbol);

Retrieves the Stock structure for the specified stock

These functions naturally depend on a struct that mirrors the database schema for the stock quotes.

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