Module 4: Coding Basics

Structs

Declaring Structs

Declaring structures in C can be done this way.

typedef struct tagTHREADENTRY32 { (1)
  DWORD   dwSize;
  DWORD   cntUsage;
  DWORD   th32ThreadID;
  DWORD   th32OwnerProcessID;
  LONG    tpBasePri;
  LONG    tpDeltaPri;
  DWORD   dwFlags;
} THREADENTRY32, *PTHREADENTRY32; (2)

1	This syntax is taken from https://learn.microsoft.com/en-us/windows/win32/api/tlhelp32/ns-tlhelp32-threadentry32
2	Uses the alias `THREADENTRY32` as the structure name and `*PTHREADENTRY32` as a pointer to that structure. Using `P` is a convention from Microsoft.

Its Rust equivalent would be.

struct THREADENTRY32 { (1)
  dwSize: u32,
  cntUsage: u32,
  th32ThreadID: u32,
  th32OwnerProcessID: u32,
  tpBasePri: i32,
  tpDeltaPri: i32,
  dwFlags: u32,
}

1	This syntax is taken from https://microsoft.github.io/windows-docs-rs/doc/windows/Win32/System/Diagnostics/ToolHelp/struct.THREADENTRY32.html

Implementing Structs

Using C

typedef struct _STRUCTURE_NAME {
  int ID;
  int Age;
} STRUCTURE_NAME, *PSTRUCTURE_NAME;


int main(int argc, char *argv[])
{
  STRUCTURE_NAME struct1 = { 0 }; (1)
  struct1.ID = 6969;
  struct1.Age = 420;

  STRUCTURE_NAME struct2 = { .ID = 6969, .Age = 420}; (2)
  PSTRUCTURE_NAME structpointer1 = &struct1; (3)
  structpointer1->Age = 421;
  (*structpointer1).Age = 422; (4)

  return 0;
}

1	Initializes all elements to 0.
2	Specifically initializes the elements. No need to specify all elements.
3	Creates a pointer to the struct which can be accessed with `→`.
4	An alternative to accessing pointer values. This is called Dereferencing Pointers.